九州大学 研究者情報
論文一覧
佐々木 一成(ササキ カズナリ) データ更新日:2021.06.11

教授 /  工学研究院 機械工学部門 水素利用工学


原著論文
1. George F. HARRINGTON, Sunho KIM, Kazunari SASAKI, Harry L. TULLER, Steffen GRIESHAMMER, Strain-modified Ionic Conductivity in Rare-earth Substituted Ceria: Effects of Migration Direction, Barriers, and Defect-interactions, J. Mater. Chem. A , 10.1039/D0TA12150A, 9, 8630-8643, 9, pp. 8630-8643, 2021.03.
2. Vanja Subotić, Shorato FUTAMURA, George F. HARRINGTON, Junko MATSUDA, Katsuya NATSUKOSHI, Kazunari SASAKI, Towards Understanding of Oxygen Electrode Processes during Solid Oxide Electrolysis Operation to Improve Simultaneous Fuel and Oxygen Generation, J. Power Sources, 10.1016/j.jpowsour.2021.229600, 492, 229600, 492, 229600, 2021.02.
3. Junko MATSUDA, Tomokazu YAMAMOTO, Shinji TAKAHASHI, Hiroshi NAKANISHI, Kazunari SASAKI, Syo MATSUMURA, In Situ TEM Investigation of Structural Changes in Ni Nanoparticle Catalysts under Gas Atmospheres: Implications for Catalyst Degradation, ACS Appl. Nano Mater. , 10.1021/acsanm.1c00006, 4, 2, 2175-2182, 4(2), pp.2175-2182, 2021.02.
4. Ting-Wei HUANG, Mayumi NAGAYAMA, Junko MATSUDA, Kazunari SASAKI, Akari HAYASHI, Mesoporous Carbon Fibers with Tunable Mesoporosity for Electrode Materials in Energy Devices, Molecules, 10.3390/molecules26030724, 26, 3, 724, 26(3), 724, 2021.01.
5. Thomas BAYER, Benjamin Vaughan CUNNING, Bretislav SMID, Roman SELYANCHYN, Shigenori FUJIKAWA, Kazunari SASAKI, Stephen Matthew LYTH, Spray Deposition of Sulfonated Cellulose Nanofibers as Electrolyte Membranes in Fuel Cells, Cellulose, 10.1007/s10570-020-03593-w, 28, 1355-1367, 28, pp. 1355-1367, 2021.01.
6. Byungchan HWANG, Shoichi KONDO, Takamasa KIKUCHI, Kazunari SASAKI, Akari HAYASHI, Masamichi NISHIHARA, Silicone-containing Polymer Blend Electrolyte Membranes for Fuel Cell Applications, J Appl Polym Sci., 10.1002/app.50328, 138, 18, 50328, 138(18), 50328, 2020.11.
7. Yusuke HONSHO, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Durability Analysis on PEM Water Electrolyzers against the Voltage Fluctuation of Wind Power, ECS Transactions, 10.1149/09809.0687ecst, 98, 9, 687-698, 98 (9), pp. 687-698, 2020.10.
8. Teppei IKEHARA, Zhiyun NODA, Junko MATSUDA, Masamichi NISHIHARA, Akari HAYASHI, Kazunari SASAKI, Porous Metal Support for Gas Diffusion Electrode of PEFCs, ECS Transactions, 10.1149/09809.0573ecst, 98, 9, 573-582, 98 (9), pp. 573-582 , 2020.10.
9. Tetsuya TONOSAKO, Zhiyun NODA, Junko MATSUDA, Masamichi NISHIHARA, Akari HAYASHI, Kazunari SASAKI, Pt-TiO2 Nanocomposite PEFC Electrocatalysts for High Potential Cycle Durability, ECS Transactions, 10.1149/09809.0523ecst, 98, 9, 523-533, 98 (9), pp. 523-533, 2020.10.
10. Tsubasa YOSHIZUMI, Zhiyun NODA, Junko MATSUDA, Masamichi NISHIHARA, Akari HAYASHI, Kazunari SASAKI, Nanostructuring Pt Electrocatalysts Supported on Nanocrystalline SnO2 for Polymer Electrolyte Fuel Cells, ECS Transactions, 10.1149/09809.0517ecst, 98, 9, 517-522, 98 (9), pp. 517-522, 2020.10.
11. Masahiro YASUTAKE, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Stephen M. LYTH, Kohei ITO, Akari HAYASHI, Kazunari SASAKI, Catalyst-Integrated Gas Diffusion Electrodes for Polymer Electrolyte Membrane Water Electrolysis: Porous Titanium Sheets with Nanostructured TiO2 Surfaces Decorated with Ir Electrocatalysts, J. Electrochem. Soc., 10.1149/1945-7111/abb37d, 167, 12, 124523, 167(12), 124523, 2020.09.
12. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Kazunari SASAKI, Semiconductive α-Al2O3/Sr3Al2O6 Oxide Layer Formed on Fe-Cr-Al Alloy, J. Electrochem. Soc., 10.1149/1945-7111/ababd8, 167, 12, 124505, 167(12), 124505, 2020.08.
13. Shota TAKEI, Keisuke UDA, Masaru NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Investigation of Reducing Concentration Overvoltage toward Development of Low Pt-Loading PEFC, J. Electrochem. Soc., 10.1149/1945-7111/abac28, 167, 12, 124510, 167(12), 124510, 2020.08, [URL], Membrane electrode assemblies (MEAs) with various catalyst-loading were made using a standard 46.5%Pt/KB (TEC10E50E) with the aim of developing low Pt-loading PEFCs. Since increase in concentration overvoltage for low catalyst-loading MEAs was observed, the mechanism of such increase in concentration overvoltage was considered, and then reducing concentration overvoltage was tried through two methods, by adding extra carbon and using a more hydrophobic carbon support, graphitized Ketjen black, within the cathode layer (CL). As a result, we have experimentally proven that increase in hydrophobicity of CL can promote water drain and reduce the concentration overvoltage for low catalyst-loading MEAs, and hydrophobicity is an important factor to be controlled within CL in addition to porosity..
14. Yusuke ISHIBASHI, Kohei MATSUMOTO, Shotaro FUTAMURA, Yuya TACHIKAWA, Junko MATSUDA, Stephen LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Improved Redox Cycling Durability in Alternative Ni Alloy-Based SOFC Anodes, J. Electrochem. Soc., 10.1149/1945-7111/abac87, 167, 12, 124517, 167(12), 124517, 2020.08, [URL], Repeated reduction and oxidation of metallic nickel in the anodes of solid oxide fuel cell (SOFC) causes volume changes and agglomeration. This disrupts the electron conducting network, resulting in deterioration of the electrochemical performance. It is therefore desirable to develop more robust anodes with high redox stability. Here, new cermet anodes are developed, based on nickel alloyed with Co, Fe, and/or Cr. The stable phases of these different alloys are calculated for oxidizing and reducing conditions, and their electrochemical characteristics are evaluated. Whilst alloying causes a slight decrease in power generation efficiency, the Ni-alloy based anodes have significantly improved redox cycle durability. Microstructural observation reveals that alloying results in the formation of a dense oxide film on the surface of the catalyst particle (e.g. Co-oxide or a complex Fe-Ni-Cr oxide). These oxide layers help suppress oxidation of the underlying nickel catalyst particles, preventing oxidation-induced volume changes/agglomeration, and thereby preserving the electron conducting pathways. As such, the use of these alternative Ni-alloy based cermets significantly improves the redox stability of SOFC anodes..
15. Daiki KAWACHINO, Masahioro YASUTAKE, Zhiyun NODA, Junko MATSUDA, Stephen M. LYTH, Akari HAYASHI, Kazunari SASAKI, Surface-Modified Titanium Fibers as Durable Carbon-Free Platinum Catalyst Supports for Polymer Electrolyte Fuel Cells, J. Electrochem. Soc., 10.1149/1945-7111/ab9cd4, 167, 10, 104513, 167(10), 104513, 2020.06, [URL], Carbon-based electrodes in polymer electrolyte fuel cells (PEFCs) are prone to corrosion. Therefore, alternative "carbon-free"materials are required. Here, the use of a catalyst-coated porous metal support is proposed as a gas diffusion electrode. As a proof-of-concept, commercially available porous titanium sheets comprising sintered titanium fibers are chemically etched with NaOH, followed by heat treatment. This results in the formation of oxidized titanium nanostructures (such as nanosheets and nanotubes) at the surface. Subsequently, platinum decoration is performed via arc plasma deposition (APD). This porous composite structure is then attached to the membrane, and used as the gas diffusion electrode for PEFC membrane electrode assemblies (MEAs). This concept integrates the catalyst, catalyst support, gas diffusion layer, and current collector in a single structure, cutting down on the number of cell components and reducing total device thickness. The carbon-free nature of this integrated gas diffusion electrode is demonstrated to successfully avoid carbon corrosion during start-stop potential cycling over 60,000 potential cycles. However, further improvements in initial electrochemical activity are still required..
16. Yoshio MATSUZAKI, Yuya TACHIKAWA, Yoshitaka BABA, Koki SATO, Gen KOJO, Hiroki MATSUO, Junichiro OTOMO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Suppression of Leakage Current in Proton-Conducting BaZr0.8Y0.2O3-δ Electrolyte by Forming Hole-Blocking Layer, J. Electrochem. Soc., 10.1149/1945-7111/ab904f, 167, 8, 084515, 167(8), 084515, 2020.05, [URL], Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3-δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking-layer. Lanthanum tungstate was found to play a role as unique and strong blocking-layer against the leakage current..
17. Marika MUTO, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Development of porous Pt electrocatalysts for oxygen reduction and evolution reactions, Molecules, 10.3390/molecules25102398, 25, 10, 2398, 25(10), 2398, 2020.05, [URL], Porous Pt electrocatalysts have been developed as an example of carbon-free porous metal catalysts in anticipation of polymer electrolyte membrane (PEM) fuel cells and PEM water electrolyzers through the assembly of the metal precursor and surfactant. In this study, porous Pt was structurally evaluated and found to have a porous structure composed of connected Pt particles. The resulting specific electrochemical surface area (ECSA) of porous Pt was 12.4 m2 g−1, which was higher than that of commercially available Pt black. Accordingly, porous Pt showed higher oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity than Pt black. When the activity was compared to that of a common carbon-supported electrocatalyst, Pt/ketjen black (KB), porous Pt showed a comparable ORR current density (2.5 mA cm−2 at 0.9 V for Pt/KB and 2.1 mA cm−2 at 0.9 V for porous Pt), and OER current density (6.8 mA cm−2 at 1.8 V for Pt/KB and 7.0 mA cm−1 at 1.8 V), even though the ECSA of porous Pt was only one-sixth that of Pt/KB. Moreover, it exhibited a higher durability against 1.8 V. In addition, when catalyst layers were spray-printed on the Nafion® membrane, porous Pt displayed more uniform layers in comparison to Pt black, showing an advantage in its usage as a thin layer..
18. Albert MUFUNDIRWA, George F. HARRINGTON, Mohammed S. ISMAIL, Břetislav ŠMID, Benjamin V. CUNNING, Yu SHUNDO, Mohamed POURKASHANIAN, Kazunari SASAKI, Akari HAYASHI, Stephen M. LYTH, Gram-scale Synthesis of Alkoxide-derived Nitrogen-doped Carbon Foam as a Support for Fe-N-C Electrocatalysts, NANOTECHNOLOGY, 10.1088/1361-6528/ab76ed, 31, 22, 225401, 2020.03.
19. Qing ZHAO, Cheng WANG, Haifeng WANG, Jianlong WANG, Yaping Tang, Zongqiang MAO, Kazunari SASAKI, H2‐Induced Thermal Treatment Significantly Influences the Development of a High Performance Low‐Platinum Core‐Shell PtNi/C Alloyed Oxygen Reduction Catalyst, Intl. J. Energy Research, 10.1002/er.5265, 44, 6, 4773-4783, 44 (6), pp. 4773-4783, 2020.03.
20. Yasuharu Kawabata, Tatsuya Nakajima, Kazuo Nakamura, Toru Hatae, Yuya Tachikawa, Shunsuke Taniguchi, Yoshio Matsuzaki, Kazunari Sasaki, Proposal of ultra-high-efficiency zero-emission power generation systems, Journal of Power Sources, 10.1016/j.jpowsour.2019.227459, 448, 2020.02, [URL], Solid oxide fuel cell (SOFC) and protonic ceramic fuel cell (PCFC) have strong features that enables high efficiency power generation and efficient CO2 capture. Applying these technologies to the fossil fuel and biomass power generation, we can realize ultra-high efficiency zero-emission power generation by capturing liquefied CO2 (LCO2) for easy transport and utilization (CCU) or storage(fossil fuel CCS and bio-energy CCS: BECCS). In this study, we propose LCO2 capture ultra-efficient power generation systems consist of multi-stage SOFC/PCFC, oxygen or hydrogen transport membrane, CO2 cooling and liquidizing units driven by exhaust heat and generated power by fuel cells. Net power generation efficiency is estimated through heat mass balance analysis. As the results for natural gas, proposed PCFC system is suitable and expected 64.7 %LHV net power generation efficiency with more than 99 vol% LCO2 capture. For biogas direct supply case, net power generation efficiency of proposed PCFC system is 57%LHV with 99 vol% capture of CO2 in the air. These results indicates that proposed systems have quite strong potential that enables ultra-high efficient CO2-free fossil fuel power generation with CCS and CO2-reduction biomass fuel power generation with BECCS..
21. Qing Zhao, Cheng Wang, Haifeng Wang, Jianlong Wang, Yaping Tang, Zongqiang Mao, Kazunari Sasaki, Synthesis of a high-performance low-platinum PtAg/C alloyed oxygen reduction catalyst through the gradual reduction method, New J. Chem., 10.1039/c9nj06156h, 44, 9, 3728-3736, 44, pp. 3728-3736, 2020.03.
22. K. Takino, Y. Tachikawa, K. Mori, S. M. Lyth, Y. Shiratori, S. Taniguchi, K. Sasaki, Simulation of SOFC performance using a modified exchange current density for pre-reformed methane-based fuels, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2019.12.089, 45, 11, 6912-6925, 45(11), pp. 6912-6925, 2020.02, [URL], Numerical simulations can be used to visualize and better understand various distributions such as gas concentration and temperature in solid oxide fuel cells (SOFCs) under realistic operating conditions. However, pre-existing models generally utilize an anode exchange current density equation which is valid for humidified hydrogen fuels – an unrealistic case for SOFCs, which are generally fueled by hydrocarbons. Here, we focus on developing a new, modified exchange current density equation, leading to an improved numerical analysis model for SOFC anode kinetics. As such, we experimentally determine the exchange current density of SOFC anodes fueled by fully pre-reformed methane. The results are used to derive a new phenomenological anode exchange current density equation. This modified equation is then combined with computational fluid dynamics (CFD) to simulate the performance parameters of a three-dimensional electrolyte-supported SOFC. The new modified exchange current density equation for methane-based fuels reproduces the I–V characteristics and temperature distribution significantly better than the previous models using humidified hydrogen fuel. Better simulations of SOFC performance under realistic operating conditions are crucial for the prediction and prevention of e.g. fuel starvation and thermal stresses..
23. Shiyan Feng, Shoichi Kondo, Takamasa Kikuchi, Liana Christiani, Byungchan Hwang, Kazunari Sasaki, Masamichi Nishihara, Development of a Heat-Treated Polymer-Polymer Type Charge-Transfer Blend Membrane for Application in Polymer Electrolyte Fuel Cells, ACS Applied Energy Materials, 10.1021/acsaem.9b01697, 2, 12, 8715-8723, 2(12), pp. 8715-8723, 2019.12, [URL], We developed polymer electrolyte membranes (PEMs) utilizing charge-transfer (CT) interactions for polymer electrolyte fuel cells (PEFCs). CT complex formation was applied to control the position of proton conductive groups in the membranes. To understand the effect of CT complex formation on PEM performance, heat treatment was performed to enhance the extent of CT complex formation in the membrane. In this work, sulfonated polyimide (SPI) was used as the electron-accepting polymer, while polyether-containing electron-rich dialkoxynaphthalene (Poly-DAN) was used as the electron-donating polymer. After heat treatment at 150 °C for 50 h, the concentration of CT complex in the membrane was significantly enhanced by about 13 times. Heat-treated SPI/Poly-DAN membranes showed higher mechanical strength (50.8 MPa) than Nafion 212 (15.5 MPa) and highly chemical durability compared to the untreated membrane by the synergetic effect of enhanced CT complex formation and chemical cross-linking. Heat-treated SPI/Poly-DAN membranes also showed reasonable proton conductivity (32.3 mS cm-1, 80 °C, and 90% RH), although some cross-linking occurred between sulfonic acid units due to the heat treatment process. In single cell tests, heat-treated SPI/Poly-DAN membranes had maximum power densities of 255 mW cm-2 at 80 °C and 95% RH and 59.0 mW cm-2 at 110 °C and 31% RH, indicating that these heat-treated CT complex membranes could be used for fuel cell applications..
24. Masahiro YASUTAKE, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Kohei ITO, Akari HAYASHI, Kazunari SASAKI, GDL-Integrated Electrodes with Ir-Based Electrocatalysts for Polymer Electrolyte Membrane Water Electrolysis, ECS Transactions, 10.1149/09208.0833ecst, 92, 8, 833-843, 92 (8), pp. 833-843, 2019.10.
25. Hirotoshi ODOI, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, MPL/GDL-Supported Pt Electrocatalysts for PEFCs, ECS Transactions, 10.1149/09208.0507ecst, 92, 8, 507-513, 92 (8), pp.507-513, 2019.10.
26. Tetsuya TONOSAKO, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Preparation and Electrochemical Activities of Pt-TiO2 Nanocomposite Electrocatalysts for PEFCs, ECS Transactions, 10.1149/09208.0493ecst, 92, 8, 493-505, 92 (8), pp. 493-505, 2019.10.
27. Tsubasa YOSHIZUMI, Masaru NAGAMINE, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Electrocatalysts Supported on Nanocrystalline SnO2 for Polymer Electrolyte Fuel Cells, ECS Transactions, 10.1149/09208.0479ecst, 92, 8, 479-484, 92 (8), pp.479-484, 2019.10.
28. Ting-Wei HUANG, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Development of Mesoporous Carbon Fibers for PEFC Catalyst Supports, ECS Transactions, 10.1149/09208.0571ecst, 92, 8, 571-578, 92 (8), pp.571-578, 2019.10.
29. Taichi MATOBA, Hidemasa MIYAMOTO, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Dependence of Proton Conductivity on Cathode Degradation in PEFC, ECS Transactions, 10.1149/09208.0305ecst, 92, 8, 305-316, 92 (8), pp. 305-316 , 2019.10.
30. Shota TAKEI, Keisuke UDA, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Investigation of Concentration Overvoltage Increase in Low Pt-Loading PEFC, ECS Transactions, 10.1149/09208.0293ecst, 92, 8, 293-303, 92 (8), pp. 293-303, 2019.10.
31. Hiromichi MANABE, Yoshiki NAKAZATO, Makito OKUMURA, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, General Procedure for 3-Dimensional Nanostructure Analysis of PEFC Electrocatalyst Layers, ECS Transactions, 10.1149/09208.0189ecst, 92, 8, 189-196, 92 (8), pp. 189-196, 2019.10.
32. George F. Harrington, Dmitri Kalaev, Bilge Yildiz, Kazunari Sasaki, Nicola H. Perry, Harry L. Tuller, Tailoring Nonstoichiometry and Mixed Ionic Electronic Conductivity in Pr0.1Ce0.9O2-δ/SrTiO3 Heterostructures, ACS Applied Materials and Interfaces, 10.1021/acsami.9b08864, 11, 38, 34841-34853, 11(38), pp. 34841-34853, 2019.09, [URL], The oxygen deficiency or excess, as reflected in the nonstoichiometry of oxide films, plays a crucial role in their functional properties for applications such as micro solid oxide fuel cells, catalysis, sensors, ferroelectrics, and memristors. High concentrations of oxygen vacancies may be beneficial or detrimental according to the application, and hence there is interest in controlling the oxygen content of films without resorting to compositional changes. Here, we demonstrate that substantial changes in the nonstoichiometry of Pr0.1Ce0.9O2-δ (PCO), a model mixed ionic electronic conductor, can be achieved by fabricating multilayers with an inert material, SrTiO3 (STO). We fabricated heterostructures using pulsed laser deposition, keeping the total thickness of PCO and STO constant while varying the number of layers and thickness of each individual layer, to probe the effects of the PCO/STO interfaces. Conductivity measurements as a function of oxygen partial pressure (PO2 ) and temperature showed a significant weakening of the PO2 dependence compared to bulk PCO, which scaled with the density of interfaces. We confirmed that this change was due to variations in nonstoichiometry, by optical transmission measurements, and show that the lower oxygen content is consistent with a decrease in the effective oxygen reduction enthalpy of PCO. These results exemplify the dramatic differences in properties between films and their bulk counterparts, achievable by interface engineering, and provide generalized insight into tailoring the properties of mixed ionic electronic conductors at the nanoscale..
33. Hung-Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Kazunari SASAKI, Semiconductive α-Al2O3/Sr3Al2O6 Oxide Layer Formed on Fe-Cr-Al Alloy, ECS Transactions, 10.1149/09101.2299ecst, 91, 1, 2299-2305, 91(1), pp. 2299-2305, 2019.09.
34. Shotaro FUTAMURA, Aki MURAMOTO, Yuya TACHIKAWA, Junko MATSUDA, Stephen Matthew LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, SOFC Anodes Impregnated with Noble Metal Catalyst Nanoparticles for High Fuel Utilization, ECS Transactions, 10.1149/09101.1905ecst, 91, 1, 1905-1913, 91(1), pp. 1905-1913, 2019.09.
35. Yusuke ISHIBASHI, Shotaro FUTAMURA, Yuya TACHIKAWA, Junko MATSUDA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Alternative Ni-Alloy Cermet Anode Materials for SOFCs, ECS Transactions, 10.1149/09101.1889ecst, 91, 1, 1889-1896, 91(1), pp. 1889-1896, 2019.09.
36. Yoshio MATSUZAKI, Yuya TACHIKAWA, Yoshitaka BABA, Koki SATO, Hiroki IINUMA, Gen KOJO, Hiroki MATSUO, Junichiro OTOMO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Leakage Current and Chemical Potential Profile in Proton-Conducting Bi-Layered Solid Oxide Electrolyte with BZY and Hole-Blocking Layers, ECS Transactions, 10.1149/09101.1009ecs, 91, 1, 1009-1018, 91(1), pp. 1009-1018, 2019.09.
37. Yuko INOUE, Jyh-Tyng CHOU, Tsutomu KAWABATA, Junko MATSUDA, Shunsuke TANIGUCHI, Kazunari SASAKI, Influence of Current Load on the Growth of SrZrO3 at the GDC/YSZ Interface, ECS Transactions, 10.1149/09101.0847ecst, 91, 1, 847-852, 91(1), pp. 847-852, 2019.09.
38. H. Yokokawa, M. Suzuki, M. Yoda, T. Suto, K. Tomida, K. Hiwatashi, M. Shimazu, A. Kawakami, H. Sumi, M. Ohmori, T. Ryu, N. Mori, M. Iha, S. Yatsuzuka, K. Yamaji, H. Kishimoto, K. Develos-Bagarinao, T. Shimonosono, K. Sasaki, S. Taniguchi, T. Kawada, M. Muramatsu, K. Terada, K. Eguchi, T. Matsui, H. Iwai, M. Kishimoto, N. Shikazono, Y. Mugikura, T. Yamamoto, M. Yoshikawa, K. Yasumoto, K. Asano, Y. Matsuzaki, K. Sato, T. Somekawa, Achievements of NEDO Durability Projects on SOFC Stacks in the Light of Physicochemical Mechanisms, FUEL CELLS, 10.1002/fuce.201800187, 19, 4, 311-339, 2019.08.
39. Yoshio MATSUZAKI, Yuya TACHIKAWA, Hiroki IINUMA, Koki SATO, Yoshitaka BABA, Junichiro OTOMO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Modified Energy Efficiencies of Proton‐conducting SOFCs with Partial Conductions of Oxide‐ions and Holes, Fuel Cells, 10.1002/fuce.201800181, 19, 4, 503-511, 19(4), pp. 503-511, 2019.06.
40. George F. HARRINGTON, Lixin SUN, Bilge YILDIZ, Kazunari SASAKI, Nicola H. PERRY, Harry L. TULLER, The Interplay and Impact of Strain and Defect Association on the Conductivity of Rare-earth Substituted Ceria, Acta Materialia, 10.1016/j.actamat.2018.12.058, 166, 447-458, 166, pp. 447-458, 2019.03.
41. Shotaro FUTAMURA, Aki MURAMOTO, Yuya TACHIKAWA, Junko MATSUDA, Stephen M. LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, SOFC Anodes Impregnated with Noble Metal Catalyst Nanoparticles for High Fuel Utilization, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2019.01.223, 44, 16, 8502-8518, 44(16), pp. 8502-8518, 2019.03.
42. Ting CHEN, George HARRINGTON, Juveria MASOOD, Kazunari SASAKI, Nicola PERRY, Emergence of Rapid Oxygen Surface Exchange Kinetics during in Situ Crystallization of Mixed Conducting Thin Film Oxides, ACS Applied Materials & Interfaces, 10.1021/acsami.8b21285, 11, 9, 9102-9116, 11 (9), pp 9102–9116, 2019.03.
43. Tatsuya KAWASAKI, Junko MATSUDA, Yuya TACHIKAWA, Stephen Matthew LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Oxidation-Induced Degradation and Performance Fluctuation of Solid Oxide Fuel Cell Ni Anodes under Simulated High Fuel Utilization Conditions, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2019.02.136, 44, 18, 9386-9399, 44(18), pp. 9386-9399, 2019.03.
44. T. G. H. NGUYEN, Mio SAKAMOTO, Tomomi UCHIDA, D. C. T. DOAN, M. C. DANG, Phuc Hoan TU, Kazunari SASAKI, Yusuke SHIRATORI, Development of Paper-Structured Catalyst for Application to Direct Internal Reforming Solid Oxide Fuel Cell Fueled by Biogas, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2019.02.134, 44, 21, 10484-10497, 44, pp. 10484-10497, 2019.03.
45. Yang Ming HAO, Hironori NAKAJIMA, Akiko INADA, Kazunari SASAKI, Kohei ITO, Overpotentials and Reaction Mechanism in Electrochemical Hydrogen Pumps, Electrochimica Acta, 10.1016/j.electacta.2019.01.108, 301, 274-283, 301, pp. 274-283, 2019.01.
46. H. Yokokawa, M. Suzuki, M. Yoda, T. Suto, K. Tomida, K. Hiwatashi, M. Shimazu, A. Kawakami, H. Sumi, M. Ohmori, T. Ryu, N. Mori, M. Iha, S. Yatsuzuka, K. Yamaji, H. Kishimoto, K. Develos-Bagarinao, T. Shimonosono, K. Sasaki, S. Taniguchi, T. Kawada, M. Muramatsu, K. Terada, K. Eguchi, T. Matsui, H. Iwai, M. Kishimoto, N. Shikazono, Y. Mugikura, T. Yamamoto, M. Yoshikawa, K. Yasumoto, K. Asano, Y. Matsuzaki, K. Sato, T. Somekawa, Achievements of NEDO Durability Projects on SOFC Stacks in the Light of Physicochemical Mechanisms, Fuel Cells, 10.1002/fuce.201800187, 19, 4, 311-339, 2019.01, [URL], Achievements of NEDO durability projects on SOFC mode are summarized with a focus on the physicochemical mechanisms characterized by diffusion properties of cell components and chemical reactions of cell components with gaseous impurities. Ni sintering and depletion including impurity (P, B, S) effects have been examined in terms of the surface/interface energies of Ni/oxide cermet anodes. The conductivity degradation due to the transformation of the cubic YSZ electrolyte was found to be characterized in terms of two time constants for the reductive and the oxidative regions to be determined by the Y-diffusivity and its enhancement on NiO internal reduction in YSZ, while observed gaps in conductivity degradation behavior between stacks and button cells were ascribed to differences in those physicochemical properties involved, namely cation diffusion and kinetics associated with NiO internal reduction. The cathode performance degradation due to sulfur poisoning exhibits a variety of dependences on the microstructure (dense or porous) of doped-ceria interlayers, the thickness of YSZ electrolyte and the humidity in the anode atmosphere, suggesting effects of protons in the cathode vicinity and the SrO activity changes during fabrication the LSCF/GDC/YSZ multilayers. Some defect chemical considerations were made on how such defects are affected by fabrication processes..
47. Yusuke Ishibashi, Shotaro Futamura, Yuya Tachikawa, Junko Matsuda, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari Sasaki, Alternative Ni-alloy cermet anode materials for SOFCs, 16th International Symposium on Solid Oxide Fuel Cells, SOFC 2019
Solid Oxide Fuel Cells 16, SOFC 2019
, 10.1149/09101.1889ecst, 1889-1896, 2019.01, [URL], Solid oxide fuel cell (SOFC) is a promising electrochemical energy conversion device that can directly produce electricity from chemical fuels. On the other hand, in the Ni-zirconia cermet currently used for the SOFC anode, the electron conducting pathways through the Ni metal phase can be easily destroyed by redox processes, where Ni oxidation/reduction (redox) results in significant volume changes, leading to deterioration of the electrochemical performance. In this study, various anodes using Ni-based alloys as alternative materials for Ni are prepared. Their electrochemical performance and redox stability are evaluated. In particular, Ni-Co alloy cermet exhibits better durability against redox cycling..
48. Y. Inoue, J. T. Chou, T. Kawabata, J. Matsuda, S. Taniguchi, K. Sasaki, Influence of current load on the growth of SrZrO3 at the GDC/YSZ interface, 16th International Symposium on Solid Oxide Fuel Cells, SOFC 2019
Solid Oxide Fuel Cells 16, SOFC 2019
, 10.1149/09101.0847ecst, 847-852, 2019.01, [URL], The influence of current load on the growth of SrZrO3 formed at the interface of a gadolinia-doped ceria (GDC) interlayer and yttria-stabilized zirconia (YSZ) electrolyte was analyzed using high-resolution electron microscopy. A cell with LNF (LaNi0.6Fe0.4O3) cathode was prepared after removing the LSCF cathode using HCl. The LNF cathode was used to eliminate the effect of Sr diffusion during cell operation. These cells were operated under 0.2 A cm−2 at 800°C. For the cell with the LNF cathode, no significant change was observed in the amount of SrZrO3. At the SrZrO3/GDC interface, crystal orientation was the same from the GDC side to the SrZrO3 side. Before cell operation, the GDC grain had some defects and no clear boundary was distinguished between GDC and SrZrO3. After cell operation, the SrZrO3/GDC interface was clearer and crystallization of SrZrO3 proceeded..
49. Y. Matsuzaki, Y. Tachikawa, Y. Baba, K. Sato, H. Iinuma, G. Kojo, H. Matsuo, J. Otomo, H. Matsumoto, S. Taniguchi, K. Sasaki, Leakage current and chemical potential profile in proton-conducting bi-layered solid oxide electrolyte with Bzy and hole-blocking layers, 16th International Symposium on Solid Oxide Fuel Cells, SOFC 2019
Solid Oxide Fuel Cells 16, SOFC 2019
, 10.1149/09101.1009ecst, 1009-1018, 2019.01, [URL], Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3-δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking -layer. Lanthanum tungstate was found to play a role as unique and strong blocking -layer against the leakage current..
50. Y. Matsuzaki, Y. Tachikawa, H. Iinuma, K. Sato, Y. Baba, J. Otomo, H. Matsumoto, S. Taniguchi, K. Sasaki, Modified Energy Efficiencies of Proton-conducting SOFCs with Partial Conductions of Oxide-ions and Holes, Fuel Cells, 10.1002/fuce.201800181, 19, 4, 503-511, 2019.01, [URL], An analytical method to determine the electrochemical energy efficiencies of electrolytes with partial electronic conduction has been developed previously and reported in the literature. However, this analytical method does not address the effects of differing ionic species in electrolytes, i.e., the oxide-ions or protons. Therefore, we aimed to modify this analytical method to account for the effects of differing ionic species, and applied it to compare the energy efficiencies of oxide-ion conducting solid electrolytes such as yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) to proton-conducting solid electrolytes, such as yttria-doped barium zirconate (BZY). With the modification, difference in the influence of the fuel consumption between the oxide-ion conducting electrolyte and the proton-conducting electrolyte has been successfully taken into account. The energy efficiency of the BZY electrolyte relatively increased against those of YSZ or GDC electrolytes by the modification. Additionally, partial oxide-ion conduction in the proton-conducting electrolyte was successfully estimated using the modified analytical method..
51. Ting Chen, George F. Harrington, Junko Matsuda, Kazunari Sasaki, David Pham, Erica L. Corral, Nicola H. Perry, Modifying grain boundary ionic/electronic transport in nano-Sr- And Mg- Doped LaGAO3-δ by sintering variations, Journal of the Electrochemical Society, 10.1149/2.0151910jes, 166, 10, F569-F580, 2019.01, [URL], Perovskite La0.9Sr0.1Ga0.9Mg0.1O3-δ (LSGM) is one of the fastest known oxide ion conductors, with reported enhanced p-type electronic transference numbers at grain boundaries, attributed to space charge effects. As this material is applied as a solid oxide fuel/electrolysis cell electrolyte, it is of interest to learn how its mixed conductivity may be tailored. Field assisted sintering technique/spark plasma sintering (FAST/SPS) and conventional sintering without field or pressure were employed to prepare pellets with various grain sizes, in order to systematically assess the influence of processing route on the mixed conductivity. AC-impedance spectroscopy and the brick layer model were applied to determine local conductivities as a function of temperature, oxygen partial pressure, and dc bias. With increasing sintering temperature and grain size, the following trends were observed: larger electrical grain boundary (GB) widths, higher GB potentials, lower specific GB conductivity, greater dc-bias dependence of GB conductivity, higher pO2-dependence of GB conductivity indicating higher electronic transference numbers, and lower pre-exponential factor for specific GB conductivity. These results suggest an increasing GB space charge effect with increasing sintering temperature/grain size, which coincided with increasing compositional uniformity by TEM and EDS. The results confirm that sintering route is an important variable for tailoring mixed conduction..
52. S. Futamura, A. Muramoto, Y. Tachikawa, J. Matsuda, S. M. Lyth, Y. Shiratori, S. Taniguchi, K. Sasaki, SOFC anodes impregnated with noble metal catalyst nanoparticles for high fuel utilization, 16th International Symposium on Solid Oxide Fuel Cells, SOFC 2019
Solid Oxide Fuel Cells 16, SOFC 2019
, 10.1149/09101.1905ecst, 1905-1913, 2019.01, [URL], In order to improve the stability under high fuel utilization, alternative anodes are fabricated with ionic (mixed) conducting GDC (Ce0.9Gd0.1O2) and electronic conducting LST (Sr0.9La0.1TiO3), both of which act as stable ion- and electron-conducting frameworks against reduction-oxidation (redox) cycles, respectively. Noble metal catalyst nanoparticles (Rh, Pt, or Pd) are incorporated via impregnation with GDC on the LST-GDC backbones. The electrochemical characteristics, such as the stability against redox cycling and under high fuel utilization, of SOFC single cells using these anodes are characterized in humidified H2 at 800°C. Moreover, the changes of the noble metal catalyst nanoparticles before/after the high fuel utilization durability tests are analyzed and discussed..
53. H. C. Pham, S. Taniguchi, Y. Inoue, J. T. Chou, K. Sasaki, Semiconductive α-Al2O3/Sr3Al2O6 Oxide Layer formed on Fe-Cr-Al Alloy, 16th International Symposium on Solid Oxide Fuel Cells, SOFC 2019
Solid Oxide Fuel Cells 16, SOFC 2019
, 10.1149/09101.2299ecst, 2299-2305, 2019.01, [URL], Surface oxide layer of Fe-Cr-Al alloy was investigated to apply for metal support material of SOFCs. We already found that electrical resistance of the surface oxide layer can be decreased by La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) coating and heat-treatment. The morphology of the surface oxide layer changed to a columnar structure consisting of γ-Al2O3 polycrystal and Sr3Al2O6 growing outward in the same direction. In this study, we investigated heat-treatment condition to increase durability of the oxide layer. The Fe-Cr-Al alloy was firstly coated with LSCF and pre-heat treated in a vacuum at 1000oC for 1 h. Stability of mass gain and electrical resistance in air at 700oC was significantly improved. The morphology of the surface oxide layer was a complex structure consisting of α-Al2O3/Sr3Al2O6..
54. Daiki KAWACHINO, Masahiro YASUTAKE, Hirotoshi ODOI, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Carbon-free all-in-one electrode using porous Ti sheet for PEFCs, ECS Transactions, 10.1149/08613.0541ecst, 86, 13, 541-547, 86 (13), pp. 541-547, 2018.10.
55. Hiromichi MANABE, Yoshiki NAKAZATO, Makito OKUMURA, Junko MATSUDA, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, FIB-SEM 3-Dimensional Nanostructure Observation of PEFC Electrocatalyst Layers, ECS Transactions, 10.1149/08613.0069ecst, 86, 13, 69-75, 86 (13), pp. 69-75, 2018.10.
56. Masaru NAGAMINE, Zhiyun NODA, Hiromichi MANABE, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Oxide-core Pt-shell Electrocatalysts for PEFCs: Photochemical Preparation Using SnO2 Nanoparticles, ECS Transactions, 10.1149/08613.0531ecst, 86, 13, 531-540, 86 (13), pp. 531-540, 2018.10.
57. Hirotoshi ODOI, Zhiyiun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Pt-decorated oxide/MPL/GDL-supported PEFCs, ECS Transactions, 10.1149/08613.0461ecst, 86, 13, 461-468, 86 (13), pp. 461-468, 2018.10.
58. Msahiro YASUTAKE, Hiroki ANAI, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Kohei ITO, Akari HAYASHI, Kazunari SASAKI, Metal-Oxide-Supported Ir-decorated Electrocatalysts for Polymer Electrolyte Membrane Water Electrolysis, ECS Transactions, 10.1149/08613.0673ecst, 86, 13, 673-682, 86 (13), pp. 673-682, 2018.10.
59. Keisuke UDA, Zhiyun NODA, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Designing Cathode Layers for PEFC with the Low Platinum-Loading, ECS Transactions, 10.1149/08613.0497ecst, 86, 13, 497-506, 86 (13), pp. 497-506, 2018.10.
60. Marika MUTO, Mayumi NAGAYAMA, Kazunari SASAKI, Akari HAYASHI, Development and Evaluation of Ir Based Anode Electrocatalysts for Water Electrolysis, ECS Transactions, 10.1149/08613.0719ecst, 86, 13, 719-726, 86 (13), pp. 719-726 , 2018.10.
61. Yoshiki NAKAZATO, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Stephen M. LYTH, Akari HAYASHI, Kazunari SASAKI, PEFC Electrocatalysts Supported on Nb-SnO2 for MEAs with High Activity and Durability: Part I. Application of Different Carbon Fillers, J. Electrochem. Soc., 10.1149/2.0311814jes, 165, 14, F1154-F1163, 165 (14), pp. F1154-F1163, 2018.10.
62. Shohei MATSUMOTO, Masaru NAGAMINE, Zhiyun NODA, Junko MATSUDA, Stephen M. LYTH, Akari HAYASHI, Kazunari SASAKI, PEFC Electrocatalysts Supported on Nb-SnO2 for MEAs with High Activity and Durability: Part II. Application of Bimetallic Pt-Alloy Catalysts, J. Electrochem. Soc., 10.1149/2.0321814jes, 165, 14, F1164-F1175, 165 (14), pp. F1164-F1175, 2018.10.
63. Yuya TACHIKAWA, Yoshio MATSUZAKI, Takaaki SOMEKAWA, Koki SATO, Shunsuke TANIGUCHI, Kazunari SASAKI, Solid Oxide Electrolyzer Devices using Proton and Oxide-ion Conducting Electrolyte, Proceedings of 13th European SOFC & SOE Forum (EFCF2018), 05, A12, 160/174-174/174, Chapter 05, A12, 160/174-174/174, 2018.07.
64. Kimito KAWAMURA, Kenichiro TAKEDA, Toshihiro OSHIMA, Tsutomu KAWABATA, Shunsuke TANIGUCHI, Tomomasa KANDA, Kazunari SASAKI, Development of an SOFC Power Generation System using Carbon-Neutral Biogas, Proceedings of 13th European SOFC & SOE Forum (EFCF2018), 05, A11, A12, 160/174-166/174, Chapter 05, A11, A12, 160/174-166/174, 2018.07.
65. Yoshio MATSUZAKI, Yuya TACHIKAWA, Hiroki IINUMA, Koki SATO, Yoshitaka BABA, Junichiro OTOMO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Modified Energy Efficiencies of Proton-conducting SOFCs with Partial Conductions of Oxide-ions and Holes, Proceedings of 13th European SOFC & SOE Forum (EFCF2018), 07, A15, 40/142-49/142, Chapter 07, A15, 40/142-49/142 , 2018.07.
66. Tobias M. HUBER, Edvinas NAVICKAS, Kazunari SASAKI, Bilge YILDIZ, Herbert HUTTER, Harry TULLER, Juergen FLEIG, Interplay of Grain Size Dependent Electronic and Ionic Conductivity in Electrochemical Polarization Studies on Sr-Doped LaMnO3 (LSM) Thin Film Cathodes, J. Electrochem. Soc., 10.1149/2.1081809jes, 165, 9, F702-F709, 165 (9), pp. F702-F709, 2018.06.
67. Shiyan FENG, Shoichi KONDO, Takahiro KASEYAMA, Taichi NAKAZAWA, Takamasa KIKUCHI, Roman SELYANCHYN, Shigenori FUJIKAWA, Liana CHRISTIANI, Kazunari SASAKI, Masamichi NISHIHARA, Characterization of Polymer-Polymer Type Charge-Transfer (CT) Blend Membranes for Fuel Cell Application, Data in Brief, 10.1016/j.dib.2018.02.031, 18, 22-29, 18, pp. 22-29 , 2018.06.
68. Junko MATSUDA, Tatsuya KAWASAKI, Shotaro FUTAMURA, Tsutomu KAWABATA, Shunsuke TANIGUCHI, Kazunari SASAKI, In situ Transmission Electron Microscopic Observations of Redox Cycling of a Ni–ScSZ Cermet Fuel Cell Anode, Microscopy, 10.1093/jmicro/dfy025, 67, 5, 251-258, 67 (5) , pp. 251-258, 2018.05.
69. T. G.H. NGUYEN, D. L. TRAN, Mio SAKAMOTO, Tomomi UCHIDA, Kazunari SASAKI, T. D. To, D. C.T. Doan, M. C. Dang, Yusuke SHIRATORI, Ni-loaded (Ce,Zr)O2–Δ-dispersed Paper-structured Catalyst for Dry Reforming of Methane, Intl. J.Hydrogen Energy, 10.1016/j.ijhydene.2018.01.118, 43, 10, 4951-4960, 43(10), pp. 4951-4960, 2018.03.
70. Albert MUFUNDIRWA, George F. HARRINGTON, Bretislav SMID, Benjamin V. CUNNING, Kazunari SASAKI, Stephen M. LYTH, Durability of Template-free Fe-N-C Foams for Electrochemical Oxygen Reduction in Alkaline Solution, J. Power Sources, 10.1016/j.jpowsour.2017.07.025, 375, 244-254, 375(31), pp. 244-254, 2018.02.
71. Shiyan FENG, Shoichi KONDO, Takahiro KASEYAMA, Taichi NAKAZAWA, Takamasa KIKUCHI, Roman SELYANCHYN, Shigenori FUJIKAWA, Liana CHRISTIANI, Kazunari SASAKI, Masamichi NISHIHARA, Development of Polymer-polymer Type Charge-transfer Blend Membranes for Fuel Cell Application, J. Membr. Sci, 10.1016/j.memsci.2017.11.025, 548, 223-231, 548, pp. 223-231, 2018.02.
72. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Junko MATSUDA, Jyh-Tyng CHOU, K. MATSUOKA, Kazunari SASAKI, Durability of LSCF-coated Fe-Cr-Al Alloy for SOFC Applications, J. Electrochem. Soc., 10.1149/2.0791803jes, 165, 3, F181-F188, 165(3), pp. F181-F188, 2018.02.
73. Jyh Tyng Chou, Yuko Inoue, Tsutomu Kawabata, Junko Matsuda, Shunsuke Taniguchi, Kazunari Sasaki, Mechanism of SrZrO3 formation at GDC/YSZ interface of SOFC cathode, Journal of the Electrochemical Society, 10.1149/2.0551811jes, 165, 11, F959-F965, 2018.01, [URL], SrZrO3 formation at the interface of gadolinia-doped ceria (GDC) interlayer and yttria-stabilized zirconia (YSZ) electrolyte is analyzed using high-resolution electron microscopy. SrZrO3 is dispersed in the inter-diffusion layer on the GDC side from the Ce/Zr border. Zr, which diffuses into the GDC grain, contributes to the formation of SrZrO3. The crystallographic relationship among the SrZrO3 grains and its neighboring GDC grains reveals that SrZrO3 is formed at the surface, at the grain boundary, and inside the grain, while maintaining a highly matched boundary with the adjacent GDC grain. The matching of the interface boundary is confirmed by the O-lattice theory, according to which the threshold Zr/Ce ratio is 13/34. If Zr/Ce ratio in the GDC grain is higher than the threshold, SrZrO3 may significantly grow into the grain. The conduction path for the oxygen ion is retained because the GDC grain containing Zr is split into the SrZrO3 grain and the less-Zr-containing GDC grain. If Zr/Ce ratio is lower than the threshold, SrZrO3 may be formed but will be limited by the amount of Zr diffusing from the adjacent region. Thus, the morphology of SrZrO3 is strongly affected by the state of GDC grains in the inter-diffusion layer..
74. H. Odoi, Z. Nöda, J. Matsuda, A. Hayashi, K. Sasaki, Pt-decorated oxide/MPL/GDL-supported PEFCs, Symposium on Polymer Electrolyte Fuel Cells and Electrolyzers 18, PEFC and E 2018 - AiMES 2018, ECS and SMEQ Joint International Meeting
ECS Transactions
, 10.1149/08613.046ecst, 461-468, 2018.01, [URL], In order to improve the mass productivity of polymer electrolyte fuel cells (PEFCs), it is useful to have a fully-integrated structure from electrocatalysts to gas diffusion layer. Although carbon support is widely used for PEFCs, carbon corrosion may occur on the cathode side. To solve these technological issues, in this study, non-carbon support is directly prepared on the microporous layer (MPL) coated on the gas diffusion layer (GDL) by arc plasma deposition (APD). Pt catalyst nanoparticles are then deposited by the APD on the non-carbon support to prepare a "Pt/non-carbon support/MPL/GDL" integrated structure. Microstructure of the electrocatalyst layers and electrochemical properties of such MEAs are analyzed..
75. Aki MURAMOTO, Yudai KIKUCHI, Yuya TACHIKAWA, Stephen M. LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, High-pressure C-H-O diagrams: Fuel Composition, Carbon Deposition, and Open Circuit Voltage of Pressurized SOFCs, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2017.10.122, 42, 52, 30769-30786, 42(52), pp. 30769-30786, 2017.12.
76. Liana CHRISTIANI, Kazunari SASAKI, Masamichi NISHIHARA, Aliphatic SPI Charge-transfer Complex Hybrid Films for High Temperature Polymer Electrolyte Membrane Fuel Cells, J. Appl. Polym. Sci., 10.1002/app.46087, 135, 14, 46087, 135(14 ), pp. 46087, 2017.12.
77. Thomas BAYER, Roman SELYANCHYN, Shigenori FUJIKAWA, Kazunari SASAKI, Stephen M. LYTH, Spray-painted Graphene Oxide Membrane Fuel Cells, J. Membr. Sci, 10.1016/j.memsci.2017.07.012, 541, 347-357, 541, pp. 347-357, 2017.11.
78. Xuesong SHEN, Ting CHEN, Sean R. BISHOP, Nicola H. PERRY, Harry L. TULLER, Kazunari SASAKI, Redox Cycling Induced Ni Exsolution in Gd0.1Ce0.8Ni0.1O2-(Sr0.9La0.1)0.9Ti0.9Ni0.1O3 Composite Solid Oxide Fuel Cell Anodes, J. Power Sources, 10.1016/j.jpowsour.2017.10.009, 370, 122-130, 370, pp.122-130, 2017.10.
79. Masaru NAGAMINE, Zhiyun NODA, Shohei MATSUMOTO, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Photochemical Preparation of Pt Electrocatalysts on SnO2 Support for PEFCs, ECS Transactions, 10.1149/08008.0773ecst, 80, 8, 773-780, 80 (8), pp. 773-780, 2017.10.
80. Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Ti-Porous-Sheet-Supported Pt Electrocatalysts for PEFCs, ECS Transactions, 10.1149/08008.0781ecst, 80, 8, 781-787, 80 (8), pp. 781-787, 2017.10.
81. Keisuke UDA, Zhiyun NODA, Kazunari SASAKI, Akari HAYASHI, Electrochemical Characterization of MEAs with Different Pt-loading for the Efficient Use of Pt, ECS Transactions, 10.1149/08008.0789ecst, 80, 8, 789-799, 80 (8), pp. 789-799, 2017.10.
82. Yoshiki NAKAZATO, Daiki KAWACHINO, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, SnO2-Supported Electrocatalysts on Various Conductive Fillers for PEFCs, ECS Transactions, 10.1149/08008.0897ecst, 80, 8, 897-906, 80 (8), pp. 897-906 , 2017.10.
83. Shohei MATSUMOTO, Masaru NAGAMINE, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Development of PEFC Alloy Electrocatalysts Supported on SnO2, ECS Transactions, 10.1149/08008.0907ecst, 80, 8, 907-918, 80 (8), pp. 907-918 , 2017.10.
84. Dang Long TRAN, Quang Tuyen TRAN, Mio SAKAMOTO, Kazunari SASAKI, Yusuke SHIRATORI, Modelling of CH4 Multiple-reforming within the Ni-YSZ Anode of a Solid Oxide Fuel Cell, J. Power Sources, 10.1016/j.jpowsour.2017.05.077, 359, 507-519, 359, pp. 507-519, 2017.08.
85. H. Yokokawa, Y. Hori, T. Shigehisa, M. Suzuki, S. Inoue, T. Suto, K. Tomida, M. Shimazu, A. Kawakami, H. Sumi, M. Ohmori, N. Mori, T. Iha, K. Yamaji, H. Kishimoto, K. Develos-Bagarinao, Kazunari Sasaki, Shunsuke Taniguchi, T. Kawada, M. Muramatsu, K. Terada, K. Eguchi, T. Matsui, H. Iwai, M. Kishimoto, N. Shikazono, Y. Mugikura, T. Yamamoto, M. Yoshikawa, K. Yasumoto, K. Asano, Y. Matsuzaki, S. Amaha, T. Somekawa, Recent Achievements of NEDO Durability Project with an Emphasis on Correlation Between Cathode Overpotential and Ohmic Loss, Fuel Cells, 10.1002/fuce.201600186, 17, 4, 473-497, 17 (4), pp. 473-497, 2017.08.
86. Makito OKUMURA, Zhiyun NODA, Junko MATSUDA, Yuya TACHIKAWA, Masamichi NISHIHARA, Stephen M. LYTH, Akari HAYASHI, Kazunari SASAKI, Correlating Cathode Microstructure with PEFC Performance using FIB-SEM and TEM, J. Electrochem. Soc., 10.1149/2.0581709jes, 164, 9, F928-F934, 164 (9), pp. F928-F934, 2017.07.
87. Yoshio MATSUZAKI, Yuya TACHIKAWA, Takaaki SOMEKAWA, Koki SATO, Yasuharu KAWABATA, Mariko SUGAHARA, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Relationship between Electrochemical Properties and Electrolyte Partial Conductivities of Proton-Conducting
Ceramic Fuel Cells, ECS Transactions, 10.1149/07801.0441ecst, 78, 1, 441-450, 78 (1), pp. 441-450, 2017.07.
88. Keisuke TAKINO, Yuya TACHIKAWA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Effect of Exchange Current Density on Current Distribution at Planar-Type SOFC Anodes, ECS Transactions, 10.1149/07801.1523ecst, 78, 1, 1523-1531, 78 (1), pp. 1523-1531, 2017.07.
89. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Ting CHOU, Junko MATSUDA, Kazunari SASAKI, Investigation of Fe-Cr-Al Alloy for Metal Supported SOFC, ECS Transactions, 10.1149/07801.2069ecst, 78, 1, 2069-2075, 78 (1), pp. 2069-2075, 2017.07.
90. Aki MURAMOTO, Yudai KIKUCHI, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI , Fuel Composition in Pressurized SOFCs, ECS Transactions, 10.1149/07801.2497ecst, 78, 1, 2497-2504, 78 (1), pp. 2497-2504, 2017.07.
91. Yasuharu KAWABATA, Yoshio MATSUZAKI, Yuya TACHIKAWA, Shunsuke TANIGUCHI, Kazunari SASAKI, New Applications of SOFC-MGT Hybrid Power Generation System for Low-Carbon Society, ECS Transactions, 10.1149/07801.0197ecst, 78, 1, 197-208, 78 (1), pp. 197-208, 2017.07.
92. Junko MATSUDA, Shu KANAE, Tsutomu KAWABATA, Jyh-Tyng CHOU, Yuko INOUE, Shunsuke TANIGUCHI, Kazunari SASAKI, TEM and ETEM Study on SrZrO3 Formation at the LSCF/GDC/YSZ Interfaces, ECS Transactions, 10.1149/07801.0993ecst, 78, 1, 993-1001, 78 (1), pp. 993-1001, 2017.07.
93. Nguyen Thi G. HUONG, T. D. To, Mio SAKAMOTO, T. D. C. Doan, C. M. Dang, Tuyen Quang TRAN, Kazunari SASAKI, Yusuke SHIRATORI, Development of Flexible Catalyst Material for Internal Dry Reforming, ECS Transactions, 10.1149/07801.2431ecst, 78, 1, 2431-2439, 78 (1), pp. 2431-2439, 2017.07.
94. Shotaro FUTAMURA, Yuya TACHIKAWA, Junko MATSUDA, Stephen M. LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Alternative SOFC Anode Materials with Ion– and Electron–Conducting Backbones for Higher Fuel Utilization, ECS Transactions, 10.1149/07801.1179ecst, 78, 1, 1179-1187, 78 (1), pp. 1179-1187, 2017.07.
95. Yudai KIKUCHI, Junko MATSUDA, Yuya TACHIKAWA, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Kazunari SASAKI, Degradation of SOFCs by Various Impurities: Impedance Spectroscopy and Microstructural Analysis, ECS Transactions, 10.1149/07801.1253ecst, 78, 1, 1253-1260, 78 (1), pp. 1253-1260 , 2017.07.
96. Yuya TACHIKAWA, Yoshio MATSUZAKI, Yasuharu KAWABATA, Mariko SUGAHARA, Takaaki SOMEKAWA, Shunsuke TANIGUCHI, Kazunari SASAKI, Effect of Carbon-Neutral Fuel Fed Solid Oxide Fuel Cell System on CO2 Emission Reduction, ECS Transactions, 10.1149/07801.2563ecst, 78, 1, 2563-2568, 78 (1), pp. 2563-2568, 2017.07.
97. Dan Long TRAN, Atsushi KUBOTA, Mio SAKAMOTO, Tuyen Quang TRAN, Kazunari SASAKI, Yusuke SHIRATORI, Advanced Direct Internal Reforming Concepts for Solid Oxide Fuel Cells Running with Biogas, ECS Transactions, 10.1149/07801.2467ecst, 78, 1, 2467-2476, 78 (1), pp. 2467-2476, 2017.07.
98. Shotaro FUTAMURA, Yuya TACHIKAWA, Junko MATSUDA, Stephen M. LYTH, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Alternative Ni-Impregnated Mixed Ionic-Electronic Conducting Anode for SOFC Operation at High Fuel Utilization, J. Electrochem. Soc., 10.1149/2.0071710jes, 164, 10, F3055-F3063, 164 (10), pp. F3055-F3063, 2017.06.
99. Takaaki SOMEKAWA, Yoshio MATSUZAKI, Mariko SUGAHARA,Yuya TACHIKAWA, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Physicochemical Properties of Ba(Zr,Ce)O3-d-based Proton-Conducting Electrolytes for Solid Oxide Fuel Cells in Terms of Chemical Stability and Electrochemical Performance, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2017.04.267, 42, 16722-16730, 42, pp.16722 -16730, 2017.06.
100. Tobias M. HUBER, Edvinas NAVICKAS, Kazunari SASAKI, Bilge YILDIZ, Harry TULLER, Gernot FRIEDBACHER, Herbert HUTTER, Juergen FLEIG, Experimental Design for Voltage Driven Tracer Incorporation and Diffusion Studies on Oxide Thin Film Electrodes, J. Electrochem. Soc., 10.1149/2.0711707jes, 164, 7, F809-F814, 164 (7), pp. F809-F814, 2017.05.
101. Kenshi ITAOKA, Aya SAITO, Kazunari SASAKI, Public perception on hydrogen infrastructure in Japan: Influence of rollout of commercial fuel cell vehicles, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.10.123, 42, 11, 7290-7296, 2017.03.
102. X. Shen, T. Kawabata, K. Sasaki, Redox-stable Sr0.9La0.1TiO3-supported SOFC single cells, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.11.160, 42, 10, 6941-6949, 2017.03, [URL], The stable conductive oxide Sr0.9La0.1TiO3 (SLT), instead of the conventional Ni-zirconia, is applied as supporting porous substrate for an SOFC single cell. Four different composite anode materials: Ni-SSZ (SSZ: (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01), Ni-GDC (GDC: Ce0.9Gd0.1O2), Ni-GDC-SLT, and GDC-SLT were prepared. The porous thick Sr0.9La0.1TiO3 substrate was stable enough during 50 redox cycles so that OCV showed no decrease during the cycling test. Moreover, the electrochemical performance, redox stability, and performance degradation during the cycling tests were mainly determined by the different electrical and catalytic properties of the composite anode materials..
103. J. Sugimoto, S. Futamura, T. Kawabata, S. M. Lyth, Y. Shiratori, S. Taniguchi, K. Sasaki, Ru-based SOFC anodes
Preparation, performance, and durability, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2017.01.028, 42, 10, 6950-6964, 2017.03, [URL], Ru-based solid oxide fuel cell (SOFC) cermet anodes are presented. The preparation conditions of the Ru-based anodes are adjusted by preventing the sublimation of Ru-oxides at elevated temperatures by using an oxidizing atmosphere. SOFC single cells with zirconia-electrolyte and cathode are prepared, and the electrochemical performance is examined using realistic fuels containing low concentrations of higher hydrocarbons and trace sulfur impurities. The degradation rate is relatively high under simulated high fuel utilization operating conditions. However, under the operational condition near the fuel inlet of SOFC systems, the Ru-based anode satisfies 5000-h durability by using hydrocarbon-containing fuels. While a much higher durability is needed for stationary applications, the cells with the Ru-based anode may be applicable to e.g. automobile applications with hydrocarbon-containing fuels as high internal reforming activity, carbon deposition tolerance, and sulfur impurity tolerance have been verified..
104. Zhiyun NODA, Kyohei HIRATA, Akari HAYASHI, Tooru TAKAHASHI, Naoto NAKAZATO, Kaori SAIGUSA, Atsuko SEO, Kiyoshi SUZUKI, Seiji ARIURA, Hidetoshi SHINKAI, Kazunari SASAKI, Hydrogen pump-type impurity sensors for hydrogen fuels, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.12.066, 42, 5, 3281-3293, 2017.02.
105. H. C. Pham, S. Taniguchi, Y. Inoue, J. Matsuda, J. T. Chou, Y. Misu, K. Matsuoka, K. Sasaki, Modification of Surface Oxide Layer of Fe-Cr-Al Alloy with Coating Materials for SOFC Applications, Fuel Cells, 10.1002/fuce.201600038, 17, 1, 83-89, 2017.02, [URL], We investigated the treatment of Fe-Cr-Al alloy for application in solid oxide fuel cells (SOFCs). The electrical resistance of the Al2O3-based surface oxide layer on the alloy decreased and was stable when La0.6Sr0.4Co0.2Fe0.8O3(LSCF), La0.8Sr0.2MnO3(LSM), LaNi0.6Fe0.4O3(LNF), or Pr0.8Sr0.2MnO3(PrSM) were first coated on the alloy and heat treated at 700 °C in air. The activation energy, calculated from the resistance, also suggested that the surface oxide became more conductive with treatment. The surface oxide layer after treatment had a microstructure of columns growing outward in the same direction, containing small amounts of elements such as Sr, Ni, Fe, La, Mn, and Pr. The microstructure consists of polycrystalline γ-Al2O3and small amounts of Al compounds with these elements. In the case of the LNF coating, the formation of NiAl2O4was observed.The enhanced electrical conductivity may have resulted from the arrangement of the columnar structure, along with the electronic conduction path generated by the reaction of γ-Al2O3with these elements..
106. Takaaki SOMEKAWA, Yoshio MATSUZAKI, Yuya TACHIKAWA, Shunsuke TANIGUCHI, Kazunari SASAKI, Characterization of yttrium-doped ceria with various yttrium concentrations as cathode interlayers of SOFCs, Ionics, 10.1007/s11581-016-1816-9, 23, 1, 95-103, 2017.01.
107. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Junko MATSUDA, Jyh-Tyng CHOU, Y.MISU, K.MATSUOKA, Kazunari SASAKI, Modification of Surface Oxide Layer of Fe-Cr-Al Alloy with Coating Materials for SOFC Applications, Fuel Cells, DOI: 10.1002/fuce.201600038, 17, 1, 83-89, 2017.01.
108. Sichao MA, Jianfeng LIU, Kazunari SASAKI, Stephen M. LYTH, Paul J. A. KENIS, Carbon Foam Decorated with Silver Nanoparticles for Electrochemical CO2 Conversion, Energy Technol., 10.1002/ente.201600576, 5, 1-3, 2017.01.
109. Ting Chen, George F. Harrington, Kazunari Sasaki, Nicola H. Perry, Impact of microstructure and crystallinity on surface exchange kinetics of strontium titanium iron oxide perovskite by
In situ optical transmission relaxation approach, Journal of Materials Chemistry A, 10.1039/c7ta04940d, 5, 44, 23006-23019, 2017.01, [URL], The rate of oxygen exchange at the surface of mixed conductors is a critical property impacting the performance of elevated temperature energy conversion/storage devices. Microstructural features, such as grain boundary density and crystalline quality, are expected to impact the surface exchange kinetics, but their effect has not yet been widely studied. In this work, mixed conducting perovskite SrTi0.65Fe0.35O3-δ (STF35) thin films grown by pulsed laser deposition were applied as a model system to systematically study the effect of microstructure on oxygen surface exchange kinetics. The impact of growth temperature on crystalline quality, orientation, grain size, surface roughness, and surface chemistry was evaluated by X-ray diffraction, scanning probe microscopy, transmission electron microscopy, and angle-resolved X-ray photoelectron spectroscopy (AR-XPS). A contact-free, continuous, in situ optical transmission relaxation approach was then applied to quantify the films' native surface oxygen exchange coefficients (kchem). Amorphous films, grown at low temperatures (25 °C), did not exhibit measurable oxygen exchange ability. Highly crystalline films, grown at high temperatures (800 °C), exhibited reasonable, but not optimal kchem. The most rapid kchem was found for intermediate growth conditions, i.e., for amorphous-grown thin films just after crystallization at higher temperatures (550 °C) or for films grown near (580 °C) the crystallization temperature. Combined with the AR-XPS results showing greater surface Sr concentrations in films grown at higher temperatures, results suggest rapid kchem is obtained as a trade-off between good crystalline quality and low Sr surface concentration. Degradation of kchem over time was correlated to increased Sr surface concentration. Additionally, (100)-oriented epitaxial vs. nano-columnar grained (110)-oriented thin films with excellent crystalline quality exhibited very similar kchem and aging behavior, suggesting that neither grain boundaries nor film orientation cause observable changes in surface exchange kinetics in this composition..
110. Y. Nakazato, D. Kawachino, Z. Noda, J. Matsuda, A. Hayashi, K. Sasaki, SnO2-supported electrocatalysts on various conductive fillers for PEFCs, Symposium on Polymer Electrolyte Fuel Cells 17, PEFC 2017 - 232nd ECS Meeting
ECS Transactions
, 10.1149/08008.0897ecst, 897-906, 2017.01, [URL], Electrocatalyst layers in polymer electrolyte fuel cells (PEFCs) have complicated 3-dimensional microstructure, so that control and optimization of the structure are essential for higher cell performance. Carbon black supported cathode electrocatalyst is widely used, whilst carbon black support can be degraded through electrochemical oxidation on the cathode side. In this study, stable and electronic conductive Nb-doped SnO2 support deposited on conductive carbon nanotube (CNT) filler is considered as an alternative support material for increasing cell performance. Consequently, high current-voltage (I-V) performance and voltage cycle durability of membrane electrode assemblies (MEAs) using Nb-doped SnO2 supports deposited on CNTs are successfully demonstrated under the PEFC operational condition..
111. Kazunari Sasaki, The Impact of Fuels on Solid Oxide Fuel Cell Anode Lifetime
The Relationship Between Fuel Composition, Fuel Impurities, and Anode Lifetime and Reliability, Solid Oxide Fuel Cell Lifetime and Reliability
Critical Challenges in Fuel Cells
, 10.1016/B978-0-08-101102-7.00003-9, 37-50, 2017.01, [URL], Solid oxide fuel cells (SOFCs) are the most flexible fuel cells, and internal reforming and/or simple external reforming may be possible. In this chapter, the multifuel capability of SOFCs is considered from both thermochemical and kinetic viewpoints. Equilibria in various possible SOFC fuel gases are examined. Power generation characteristics for various types of fuels are described. Extrinsic degradation affected by fuel impurities and intrinsic degradation during long-term and cycle operation are also described and discussed..
112. Jianfeng LIU, Benjamin V. CUNNING, Takeshi DAIO, Albert MUFUNDIRWA, Kazunari SASAKI, Stephen M. LYTH, Nitrogen-Doped Carbon Foam as a Highly Durable Metal-Free Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Solution, Electrochimica Acta, 10.1016/j.electacta.2016.10.090, 220, 554-561, 2016.12.
113. Shiyan FENG, Kazunari SASAKI, Masamichi NISHIHARA, Effect of Sulfonation Level on Sulfonated Aromatic Poly(ether sulfone) Membranes as Polymer Electrolyte for High-Temperature Polymer Electrolyte Membrane Fuel Cells, Macromolecular Chemistry and Physics, 10.1002/macp.201600397, 217, 24, 2692-2699, 2016.12.
114. Xuesong SHEN, Kazunari SASAKI, Robust SOFC anode materials with La-doped SrTiO3 backbone structure, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.08.024, 41, 38, 17044-17052, 2016.10.
115. Hidemasa MIYAMOTO, Masahiko KITAMURA, Zhiyun NODA, Kazunari SASAKI, Akari HAYASHI, Investigation of Problems at the PEFC Cathode Layer under Higher Temperature Operation, ECS Transactions, 75, 14, 329-337, 2016.10.
116. Makito OKUMURA, Zhiyun NODA, Junko MATSUDA, Masamichi NISHIHARA, Akari HAYASHI, Kazunari SASAKI, An FIB-SEM Study on Correlations between PEFC Electrocatalyst Microstructure and Cell Performance, ECS Transactions, 75, 14, 347-354, 2016.10.
117. Bo FU, Yasuto MINAMIDA, Zhiyun NODA, Kazunari SASAKI, Akari HAYASHI, Development of MEAs by Controlling Carbon Structures in Cathode Layers, ECS Transactions, 75, 14, 827-835, 2016.10.
118. Yoshiki NAKAZATO, Masahiro IWAMI, Makito OKUMURA, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, SnO2-Supported Electrocatalysts on Conductive Fillers for PEFCs, ECS Transactions, 75, 14, 841-849, 2016.10.
119. Shohei MATSUMOTO, Masahiro IWAMI, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, PEFC Alloy Electrocatalysts Supported on SnO2: A study on the preparation method, ECS Transactions, 75, 14, 851-858, 2016.10.
120. Hiroki ANAI, Junko MATSUDA, Zhiyun NODA, Yuya TACHIKAWA, Akari HAYASHI, Kohei ITO, Kazunari SASAKI, Preparation of Iridium/SnO2/VGCF Electrocatalysts for Water Electrolysis, ECS Transactions, 75, 14, 1129-1135, 2016.10.
121. Yan Ming HAO, Hironori NAKAJIMA, Akiko INADA, Kazunari SASAKI, Kohei ITO, Separation and Characterization of Overpotentials in Electrochemical Hydrogen Pump with a Reference Electrode, ECS Transactions, 75, 14, 1155-1163, 2016.10.
122. Takaaki SOMEKAWA, Yoshio MATSUZAKI, Yuya TACHIKAWA, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Physicochemical properties of proton-conductive Ba(Zr(0.1)Ce(0.7)Y(0.1)AYb(0.1))O3-delta solid electrolyte in terms of electrochemical performance of solid oxide fuel cells, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.07.265, 41, 39, 17539-17547, 2016.10.
123. Thomas BAYER, Hung Cuong PHAM, Kazunari SASAKI, Stephen M. LYTH, Spray deposition of Nafion membranes: Electrode-supported fuel cells, J. Power Sources, 10.1016/j.jpowsour.2016.07.059, 327, 319-326, 2016.09.
124. Ryohei Torii, Yuya Tachikawa, Kazunari Sasaki, Kohei Ito, Anode gas recirculation for improving the performance and cost of a 5-kW solid oxide fuel cell system, Journal of Power Sources, 10.1016/j.jpowsour.2016.06.045, 325, 229-237, 2016.09, [URL], Solid oxide fuel cells (SOFCs) have the potential to efficiently convert chemical energy into electricity and heat and are expected to be implemented in stationary combined heat and power (CHP) systems. This paper presents the heat balance analysis for a 5-kW medium-sized integrated SOFC system and the evaluation of the effect of anode gas recirculation on the system performance. The risk of carbon deposition on an SOFC anode due to anode gas recirculation is also assessed using the C-H-O diagram obtained from thermodynamic equilibrium calculations. These results suggest that a higher recirculation ratio increases net fuel utilization and improves the electrical efficiency of the SOFC system. Furthermore, cost simulation of the SOFC system and comparison with the cost of electricity supply by a power grid indicates that the capital cost is sufficiently low to popularize the SOFC system in terms of the total cost over one decade..
125. Yang Ming HAO, Hironori NAKAJIMA, Hiroshi YOSHIZUMI, Akiko INADA, Kazunari SASAKI, Kohei ITO, Characterization of an electrochemical hydrogen pump with internal humidifier and dead-end anode channel, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.05.160, 41, 32, 13879-13887, 2016.08.
126. Daiki ISHIBASHI, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Kazunari SASAKI, Deposition, agglomeration and vaporization of chromium oxide by cathode polarization change in SOFC cathodes, J. Electrochemical Society, DOI: 10.1149/2.0141607jes, 163, 7, F596-F602, 2016.07.
127. Xuesong SHEN, Kazunari SASAKI, Highly redox-resistant solid oxide fuel cell anode materials based on La-doped SrTiO3 by catalyst impregnation strategy, J. Power Sources, 10.1016/j.jpowsour.2016.04.111, 320, 180-187, 2016.07.
128. Thomas BAYER, Benjamin V. CUNNING, Roman SELYANCHYN, Masamichi NISHIHARA, Shigenori FUJIKAWA, Kazunari SASAKI, Stephen M. LYTH, High Temperature Proton Conduction in Nanocellulose Membranes: Paper Fuel Cells, Chem. Mater., 10.1021/acs.chemmater.6b01990, 28, 13, 4805-4814, 2016.07.
129. Takeshi DAIO, Pratoy MITRA, Stephen M. Lyth, Kazunari SASAKI, Atomic-resolution analysis of degradation phenomena in SOFCS: A case study of SO2 poisoning in LSM cathodes, Int. J. Hydrogen Energy, 10.1016/j.ijhydene.2016.05.216, 41, 28, 12214-12221, 2016.07.
130. Jianfeng LIU, Yu SHUNDO, Takeshi DAIO, Mohammed. S. ISMAIL, Kazunari SASAKI, Stephen Matthew LYTH, Metal-Free Nitrogen-Doped Carbon Foam Electrocatalysts for the Oxygen Reduction Reaction in Acid Solution, J. Electrochem. Soc., 10.1149/2.0631609jes, 163, 9, F1049-F1054, 2016.07.
131. Kazunari SASAKI, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Akari HAYASHI, Toshihiro OSHIMA, Yuya TACHIKAWA, Masamichi NISHIHARA, Junko MATSUDA, Tsutomu KAWABATA, Miki FUJITA, Ayumi ZAITSU, NEXT-FC: An SOFC-Center for Tight Industry-Academia Collaboration and Demonstration, Proceedings of 12th European SOFC & SOE Forum 2016, Chapter 02, 142-151, 2016.07.
132. Xuesong SHEN, Kazunari SASAKI, Redox-Stable SOFC Anode Materials based on La-doped SrTO3 Oxide with Impregnated Catalysts, Proceedings of 12th European SOFC & SOE Forum 2016, Chapter 11, 154-164, 2016.07.
133. Yoshio MATSUZAKI, Yuya TACHIKAWA, Takaaki SOMEKAWA, Kouki SATO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Potential for Critically-High Electrical Efficiency of Multi-Stage SOFCs with Proton-Conducting Solid Electrolyte, Proceedings of 12th European SOFC & SOE Forum 2016, Chapter 03, 195-205, 2016.07.
134. Yuya TACHIKAWA, Yoshio MATSUZAKI, Takaaki SOMEKAWA, Shunsuke TANIGUCHI, Kazunari SASAKI, Multi-Stage Highly-Efficient SOFC System using Proton and Oxide-ion Conducting Electrolyte, Proceedings of 12th European SOFC & SOE Forum 2016, Chapter 08, 258-264, 2016.07.
135. Hua LI, Akiko INADA, Tsuyohiko FUJIGAYA, Hironori NAKAJIMA, Kazunari SASAKI, Kohei ITO, Effects of operating conditions on performance of high-temperature polymer electrolyte water electrolyzer, J. Power Sources, 10.1016/j.jpowsour.2016.03.108, 318, 192-199, 2016.06.
136. Thomas BAYER, Benjamin V. CUNNING, Roman SELYANCHYN, Takeshi DAIO, Masamichi NISHIHARA, Shigenori FUJIKAWA, Kazunari SASAKI, Stephen M. LYTH, Alkaline anion exchange membranes based on KOH-treated multilayer graphene oxide, Journal of Membrane Science, 10.1016/j.memsci.2016.02.017, 508, 51-61, 2016.06.
137. Thomas BAYER, Sean R. BISHOP, Nicola H. PERRY, Kazunari SASAKI, Stephen M. LYTH, Tunable Mixed Ionic/Electronic Conductivity and Permittivity of Graphene Oxide Paper for Electrochemical Energy Conversion, ACS Appl. Mater. Interfaces, 10.1021/acsami.6b01670, 8, 18, 11466-11475, 2016.05.
138. Y. Matsuzaki, Y. Tachikawa, T. Hatae, H. Matsumoto, S. Taniguchi, K. Sasaki, Symbolic Analysis of Multi-Stage Electrochemical Oxidation for Enhancement of Electric Efficiency of SOFCs, Ceramic Transactions, 10.1002/9781119234531.ch4, 255, 41-46, 2016.05, [URL], SOFCs have the solid-state ceramic construction and operate at high-temperatures, with flexibility in fuel choice, high efficiency, stability, and reliability. The most attractive characteristics of SOFCs should be high fuel-to-electricity conversion efficiencies of as high as 50 to 60 percent LHV. For further improving the electrical efficiencies, preceding studies on multi-stage electrochemical oxidation with SOFCs have been reported. However, there are many parameters for the multi-stage oxidation, and effects of the parameters on the efficiency remains to be identified. We have investigated the multi-stage oxidation by using a symbolic analysis method. In the case of n-stage electrochemical oxidation, the fuel utilization ratio in the individual stage was found to decrease with increasing the n value at a fixed fuel utilization ratio of an entire system, resulting in the enhancement of robustness against the operation at a high fuel utilization ratio of the entire system as well as against a gas-leakage..
139. Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Development of Charge-Transfer Complex Hybrid Films as Polymer Electrolyte Membrane for High Temperature PEFC Operation, Macromolecular Chemistry and Physics, 10.1002/macp.201500320, 217, 5, 654-663, 2016.03, [URL], Novel charge-transfer (CT) complex hybrid films for high temperature polymer electrolyte fuel cell (PEFC) application based on sulfonated polyimide (SPI) with hydrophobic unit (4,4 (sulfonylbis(4,1-phenylene)bis(oxy)dianyline (BAPPS)) are synthesized and characterized. In this study, property changes of the polymer electrolytes prepared by a unique CT complex postmodification process are evaluated. The effect of the CT complex formation in the obtained films on the properties of the polymer films is evaluated, because the CT complex can work as a binder between SPIs. Water uptake of the CT complex hybrid films shows a lower value than that of the original SPI film. The CT complex hybrid films also exhibit comparable proton conductivity to Nafion 115 under high-temperature operational conditions (100-120 °C). These results suggest that the CT complex hybrid films developed are promising alternatives for high temperature PEFC application..
140. M. Okumura, Z. Noda, J. Matsuda, M. Nishihara, A. Hayashi, K. Sasaki, An FIB-SEM study on correlations between PEFC electrocatalyst microstructure and cell performance, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.0347ecst, 347-354, 2016.01, [URL], The electrocatalyst layer of the polymer electrolyte fuel cells (PEFCs) has a complicated porous microstructure. Since the porous nanostructure allows the transport of reactant gas, water vapor, protons, and electrons, cell performance depends strongly on their 3D microstructure. Understanding the correlations between the electrocatalyst microstructure and the cell performance is therefore essential for further improving the PEFC electrochemical performance. In this study, these correlations are quantitatively considered by using the focused-ion-beam coupled scanning electron microscopy (FIB-SEM) technique. In particular, while it is difficult to distinguish between the solid and the pore of the electrocatalyst layer due to the complicated porous nanostructure, this problem has been solved by the auto-image thresholding technique..
141. Daiki Ishibashi, Shunsuke Taniguchi, Yuko Inoue, Jyh Tyng Chou, Kazunari Sasaki, Deposition, agglomeration and vaporization of chromium oxide by cathode polarization change in SOFC cathodes, Journal of the Electrochemical Society, 10.1149/2.0141607jes, 163, 7, F596-F602, 2016.01, [URL], The mechanism of Cr deposition was investigated using NiO/YSZ or NiO/GDC composite cathodes, controlling cathode polarization, and observing the change in Cr distribution. By applying cathode polarization at 200 mV, Cr deposited on the surface of the electrolyte (YSZ or GDC) near the electrode reaction site similarly to the case of typical LSM cathodes. In these cathodes consisting of NiO, the Cr deposition occurred only on the electrolyte surface. After removing the polarization, the deposited Cr partially detached from the electrolyte surface and agglomerated as crystalline Cr2O3 at the interface between NiO and the electrolyte. The deposited Cr may decrease over time by continuous vaporization, and may be agglomerated to form crystalline Cr2O3 transiently. The disappearance of Cr was faster for the NiO/GDC cathode than for the NiO/YSZ cathode. By applying reverse polarization at -200 mV for 1 h, the deposited Cr disappeared from the electrolyte surface for both cathodes. Therefore, the deposition of Cr on the electrolyte seems to be a reversible reaction..
142. Bo Fu, Yasuto Minamida, Zhiyun Noda, Kazunari Sasaki, Akari Hayashi, Development of MEAs by controlling carbon structures in cathode layers, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.0827ecst, 827-835, 2016.01, [URL], Pt nanoparticles have been encapsulated into nano-channels of mesoporous carbon (MC), in order to suppress the mobility of Pt particles and then increase the durability. For further enhancing IV performance, especially in the high current density region, addition of carbon nanofiber (CNF) to the cathode catalyst layers was explored, and an optimal condition was evaluated. As a result, MEA with 10 wt.% CNF addition showed the highest IV performance even though porosity itself was better for 20 wt.% CNF addition. Therefore, thickness is another important factor in addition to porosity, especially in terms of Pt active sites per unit thickness..
143. Hidemasa Miyamoto, Masahiko Kitamura, Zhiyun Noda, Kazunari Sasaki, Akari Hayashi, Investigation of problems at the PEFC cathode layer under higher temperature operation, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.0329ecst, 329-337, 2016.01, [URL], Toward the development of electrocatalysts for future higher temperature PEFCs, extraction of critical issues for higher temperature PEFCs was aimed. Degradation phenomena and mechanisms at 105°C were evaluated for both Aquivion® MEA and Nafion® MEA. The correlation between proton conductivity and changes in cathode structures on the acceleration degradation test was studied in detail. As a result, even though the macroporous structure of the cathode layer was homogeneous in Aquivion® MEA, larger pores almost intensely formed near the Nafion® membrane side. We have found that the carbon oxidation reaction is deeply related to H2O produced by a fuel cell reaction if it is under the low humidification condition. Therefore, when proton conductivity is low like Nafion® MEA, H2O is mainly generated at the interface between the cathode layer and Nafion® membrane and carbon oxidation intensely occurs at the interface..
144. S. Matsumoto, M. Iwami, Z. Noda, J. Matsuda, A. Hayashi, K. Sasaki, PEFC alloy electrocatalysts supported on SnO2
A study on the preparation method, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.0851ecst, 851-858, 2016.01, [URL], Pt/C is widely used as a PEFC electrocatalyst. However, Pt detachment and aggregation due to carbon corrosion can occur. Therefore, the conventional Pt/Celectrocatalysthas a difficulty in durability.Our research group have developed Pt/SnO2/VGCF-H electrocatalystsand achieved both high catalyticactivity and high voltage-cycle durability. In this study,we have focusedon PtxCoyalloying anddevelopedPtxCoy/Nb-SnO2/VGCF-H electrocatalystsin order to achieve higher oxygen reduction reaction (ORR)activity. XRD measurementsexhibited alloying of PtxCoybut not reduced SnO2. In addition, half-cell measurements revealedthat a high ORRactivity due to possible PtxCoyalloyinghas been achievedafterperforming the proper heat treatment..
145. H. Anai, J. Matsuda, Z. Noda, Y. Tachikawa, A. Hayashi, K. Ito, K. Sasaki, Preparation of iridium/SnO2/VGCF electrocatalysts for water electrolysis, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.1129ecst, 1129-1135, 2016.01, [URL], Novel iridium-basedelectrocatalysts supported on SnO2/Vapor-Grown Carbon Fiber (VGCF)havebeendevelopedand characterized by FESEM, STEM, and XPS.The membraneelectrode assembly (MEA)made withtheIrO2/Sn0.98Nb0.02O2/VGCFelectrocatalystexhibited a decrease inovervoltageespeciallyunderthelow current densitycompared to the MEA made withconventionalIrO2/Ti electrocatalyst.Iridium-based SnO2/VGCF can bea good candidate for anode catalystsof water electrolysis cells..
146. T. Chen, G. F. Harrington, K. Sasaki, N. H. Perry, Relating microstructure to surface exchange kinetics using in situ optical absorption relaxation, Symposium on Electrosynthesis of Fuels 4 - PRiME 2016/230th ECS Meeting
Electrosynthesis of Fuels 4
, 10.1149/07543.0023ecst, 23-31, 2016.01, [URL], SrTio65Feo35C3.δ (STF35) thin films grown by pulsed laser deposition were applied as a model system to explore the impact of microstructure on oxygen surface exchange kinetics, of importance for solid oxide cell electrodes. The impact of growth temperature on crystalline quality, orientation, grain size, and surface roughness was evaluated. A contact-free, continuous, in situ Optical Transmission Relaxation (OTR) approach was applied to quantify the films' native surface oxygen exchange coefficients (kchem). In situ crystallization was used to obtain fast surface exchange kinetics via a dynamic nanostructuring process..
147. Yanming Hao, Hironori Nakajima, Akiko Inada, Kazunari Sasaki, Kohei Ito, Separation and characterization of overpotentials in electrochemical hydrogen pump with a reference electrode, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.1155ecst, 1155-1163, 2016.01, [URL], Overpotentials included in electrochemical hydrogen pump are separated with using a reference electrode. Separation result shows that non-ohmic overpotential in cathode is larger than that in anode. This result is also confirmed by electrochemical impedance spectra measurement, which shows impedance spectra of cathode is larger than that of anode. Volmer-Heyrovsky-Tafel mechanism is used to explain the separation result. Simulation result with using this mechanism suggests that reactions in anode and cathode are dominated by different mechanisms, and reaction rate of cathode is 2 orders of magnitude slower than that of anode..
148. Y. Nakazato, M. Iwami, M. Okumura, Z. Nod, A. Hayashi, K. Sasaki, SnO2-supported electrocatalysts on conductive fillers for PEFCs, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16
, 10.1149/07514.0841ecst, 841-849, 2016.01, [URL], Electrocatalyst layer in polymer electrolyte fuel cells (PEFCs) has complicated 3D nanostructure, and control and optimization of the structure are essential for higher cell performance. Carbon black supported cathode catalyst is widely used, whilst carbon support can be degraded through electrochemical oxidation on the cathode side. The use of Nb-doped SnO2 supports for Pt electrocatalysts prevents support corrosion, while the use of carbon nanotube (CNT) based conductive fillers assists electronic transport in the electrocatalyst layers. High I-V performance of membrane electrode assemblies (MEAs) using stable SnO2 supports deposited on conductive CNT fillers is successfully demonstrated under the strongly acidic PEFC operational condition..
149. Yuya Tachikawa, 松崎 良雄, Kazunari Sasaki, 新規材料とシステム開発の融合による革新的新規高性能SOFCの創出, Fine ceramics report, 34, 1, 27-31, 2016.
150. 松崎 良雄, Yuya Tachikawa, 染川 貴亮, 佐藤 洸基, Hiroshige Matsumoto, 谷口 俊介, Kazunari Sasaki, 電気化学的多段酸化を用いた固体酸化物形燃料電池(SOFC)による革新的高効率発電の可能性, エネルギーと動力, 66, 286, 50-57, 2016.
151. T. Somekawa, Y. Matsuzaki, Y. Tachikawa, S. Taniguchi, K. Sasaki, Study of the solid-state reaction at the interface between lanthanoid-doped ceria and yttria-stabilized zirconia for solid-oxide fuel cell applications, Solid State Ionics, 10.1016/j.ssi.2015.09.005, 282, 1-6, 2015.12, [URL], To develop more highly-efficient SOFCs, we have investigated the thickness of highly resistive layer which consist of solid solutions of CeO2-ZrO2 system generally observed between YSZ electrolyte and cathode-interlayer made of doped CeO2. In terms of the effect of the dopant in the CeO2-based interlayer materials on the thickness of the solid solution, the use of YDC or LDC for the interlayer results in a thinner solid solution compared to that obtained when a GDC interlayer was used. When adapted into SOFCs, I-V tests at 800 °C indicated that the cell with a YDC interlayer exhibited substantially better performance than the cell with a GDC interlayer..
152. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Toru IZUMI, Koji MATSUOKA, Kazunari SASAKI, Decrease in electrical resistance of surface oxide of iron-chromium-aluminium alloy by La0.6Sr0.4Co0.2Fe0.8O3 coating and heat treatment for the application of metal-supported solid oxide fuel cells, J. Power Sources, 10.1016/j.jpowsour.2015.07.096, 297, 181-187, 2015.11.
153. Makito OKUMURA, Yohei NAGAMATSU, Zhiyun NODA, Yuya TACHIKAWA, Takeshi DAIO, Akari HAYASHI, Kazunari SASAKI, A FIB-SEM Study on Correlations between PEFC Electrocatalyst Microstructure and Cell Performance, ECS Transactions, 69, 17, 709-714, 2015.10.
154. Masahiro IWAMI, Dai HORIGUCHI, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Pt-decorated TiO2 Electrocatalysts for PEFCs, ECS Transactions, 69, 17, 603-609, 2015.10.
155. Masahiko KITAMURA, Zhiyun NODA, Junko MATSUDA, Akari HAYASHI, Kazunari SASAKI, Investigation of Durability of MEAs at Higher Temperature, ECS Transactions, 69, 17, 701-708, 2015.10.
156. Takeshi DAIO, Hai-Wen LI, Takashi GONDO, Hiroya MIYAZAKI, Tatsuya IKUTA, Takashi NISHIYAMA, Koji TAKAHASHI, Yasuyuki TAKATA, Stephen M. LYTH, Kazunari SASAKI, Dynamic Gas Environmental System Development for in situ Real-time SEM Imaging under Atmospheric Pressure, Microscopy and Microanalysis, 21, 3, 1701-1702, 2015.09.
157. Yusuke SHIRATORI, Mio SAKAMOTO, Tomomi UCHIDA, Hao LE, Quang-Tuyen TRAN, Kazunari SASAKI, Hydrotalcite-dispersed paper-structured catalyst for the dry reforming of methane, Intl. J. Hydrogen Energy, 10.1016/j.ijhydene.2015.07.016, 40, 34, 10807-10815, 2015.09.
158. Liana Christiani, Sandra Hilaire, Kazunari Sasaki, Masamichi Nishihara, Erratum
Evaluation of proton conductivity of sulfonated polyimide/dihydroxy naphthalene charge-transfer complex hybrid membranes, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.27419, 53, 6, 2015.09, [URL].
159. Akari Hayashi, Katsuya Kato, Kazunari Sasaki, Immobilization of an enzyme into nano-space of nanostructured carbon and evaluation as electrochemical sensors, Journal of nanoscience and nanotechnology, 10.1166/jnn.2015.10618, 15, 9, 7395-7401, 2015.09, [URL], The aims of this study are immobilization of formaldehyde dehydrogenase (FDH) into nano-space of nanostructured carbon and evaluation as a possible sensor detecting low concentration formaldehyde. In order to understand the effect of carbon pore size on activity and stability of FDH, mesoporous carbon (MC), originally made in our lab, and commercially available ketjen black (KB) were used in this study. Enzyme activity and electrochemical sensing ability of FDH encapsulated into such two carbon materials were compared. Our original MC resulted in favourable in some evaluated conditions but not in other conditions. MC adsorbed FDH less than KB, but enzyme activity was higher on MC per FDH. Stability against methanol increased on MC, but stability against water was rather lower on MC. Electrochemical sensing ability toward formaldehyde resulted in much better on KB, which was able to detect the sub-ppb level of formaldehyde. Consequently, such dependence is resulted by available nano-space of carbon, and so tuning the pore size of carbon is an important factor in order to develop enzyme based electrochemical sensors with high sensitivity and stability..
160. Stephen M. LYTH, Wei MA, Jianfeng LIU, Takeshi DAIO, Kazunari SASAKI, Atsushi TAKAHARA, Bruno AMEDURI, Solvothermal Synthesis of Superhydrophobic Hollow Carbon Nanoparticles from a Fluorinated Alcohol, NANOSCALE, 10.1039/c5nr03484a, 7, 38, 16087-16093, 2015.08.
161. Yuya TACHIKAWA, Junki SUGIMOTO, Masaru TAKADA, Tsutomu KAWABATA, Stephen M. LYTH, Yusuke SHIRATORI, Kazunari SASAKI, In Operando Visualization of SOFC Electrodes by Thermography and Visible Light Imaging, ECS Electrochemistry Letters, 4, 11, F61-F64, 2015.08.
162. Takeshi DAIO, Aleksandar STAYKOV, Limin GUO, Jianfeng LIU, Masaki TANAKA, Stephen M. LYTH, Kazunari SASAKI, Lattice Strain Mapping of Platinum Nanoparticles on Carbon and SnO2 Supports, SCIENTIFIC REPORTS, 10.1038/srep13126, 5, 13126, 2015.08.
163. Yoshio MATSUZAKI, Yuya TACHIKAWA, Takaaki SOMEKAWA, Toru HATAE, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells, SCIENTIFIC REPORTS, 5, 12640, 2015.07, 本研究は、燃料電池の高効率化に向けたシステム解析で、市販の燃料電池と比べ、約3割の発電効率向上が望めることを示した。高温型燃料電池システムにおいて、システム安定作動のために、発電に使用しなかった燃料を構造改良で活用しつつ、材料変更による燃料の希釈化を防ぐことで、相乗的な性能向上効果が得られ、供給した燃料のエネルギーの約80%を電気に変換可能である事を示すことができた。.
164. Takeshi DAIO, Thomas BAYER, Tatsuya IKUTA, Takashi NISHIYAMA, Koji TAKAHASHI, Yasuyuki TAKATA, Kazunari SASAKI, Stephen M. LYTH, In-Situ ESEM and EELS Observation of Water Uptake and Ice Formation in Multilayer Graphene Oxide, SCIENTIFIC REPORTS, 10.1038/srep11807, 5, 11807, 2015.07.
165. T. HATAE, K. SATO, T. SOMEKAWA, Y. MATSUZAKI, S. AMAHA, M. YOSHIKAWA, Y. MUGIKURA, K. MIYARA, T. OSHIMA, S. TANIGUCHI, K. SASAKI, M. SHIMAZU, Y. TAKAHASHI, A. KAWAKAMI, N. MORI, H. YOKOKAWA, Durability Assessment of SOFC Stacks with Several Types of Structures for Thermal Cycles During Their Lifetimes on Residential Use, ECS Transactions, 68, 1, 2209-2216, 2015.07.
166. Daiki ISHIBASHI, Eunjoo PARK, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Kazunari SASAKI, Influence of Cathode Polarization Change on Chromium Deposited on Electrolyte Surface Near Cathode Reaction Sites of SOFC, ECS Transactions, 68, 1, 1031-1037, 2015.07.
167. Shu KANAE, Yasuhiro TOYOFUKU, Tsutomu KAWABATA, Yuko INOUE, Takeshi DAIO, Junko MATSUDA, Jyh-Tyng CHOU, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Microstructural Characterization of SrZrO3 Formation and the Influence to SOFC Performance, ECS Transactions, 68, 1, 2463-2470, 2015.07.
168. Tatsuya KAWASAKI, Junki SUGIMOTO, Yuya TACHIKAWA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Oxidation-induced Degradation of SOFC Ni Anodes at High Fuel Utilizations, ECS Transactions, 68, 1, 1345-1352, 2015.07.
169. Yoshio MATSUZAKI, Yuya TACHIKAWA, Toru HATAE, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, A Parametric Study of SOFC Performances with Multi-Stage Electrochemical Oxidation for Enhancement of Electric Efficiency, ECS Transactions, 68, 1, 1961-1968, 2015.07.
170. Hung Cuong PHAM, Shunsuke TANIGUCHI, Yuko INOUE, Jyh-Tyng CHOU, Toru IZUMI, Koji MATSUOKA, Kazunari SASAKI, Electrical and Oxidation Resistance of Surface Oxide of Porous Fe-Cr-Al Alloy for the Application of Metal Supported SOFCs, ECS Transactions, 68, 1, 1715-1720, 2015.07.
171. Kazunari SASAKI, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Akari HAYASHI, Toshihiro OSHIMA, Masamichi NISHIHARA, Yuya TACHIKAWA, Takeshi DAIO, Tsutomu KAWABATA, Miki FUJITA, Ayumi ZAITSU, Smart Fuel Cell Demonstration Project: A Challenge to Realize SOFC-Powered Campus, ECS Transactions, 68, 1, 171-178, 2015.07.
172. Xuesong SHEN, Kazunari SASAKI, Development of Robust SOFC Anode Materials Using La-Doped SrTiO3, ECS Transactions, 68, 1, 1447-1453, 2015.07.
173. Yuya TACHIKAWA, Tsutomu KAWABATA, Yusuke SHIRATORI, Kazunari SASAKI, Visualization of SOFC Anode by Dual Imaging Method Using Infrared and Visible Light Cameras, ECS Transactions, 68, 1, 1115-1120, 2015.07.
174. Yuya TACHIKAWA, Yoshio MATSUZAKI, Toru HATAE, Shunsuke TANIGUCHI, Kazunari SASAKI, Process Analysis for Achieving Highly Enhanced Total Efficiency on Multi-Stage Fuel Supplied SOFC System, ECS Transactions, 68, 1, 3107-3113, 2015.07.
175. Yoshio MATSUZAKI, Yuya TACHIKAWA, Takaaki SOMEKAWA, Toru HATAE, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells, SCIENTIFIC REPORTS, 10.1038/srep12640, 5, 12640, 2015.07.
176. Tran Quang-Tuyen, Taku Kaida, Mio Sakamoto, Kazunari Sasaki, Yusuke Shiratori, Effectiveness of paper-structured catalyst for the operation of biodiesel-fueled solid oxide fuel cell, Journal of Power Sources, 10.1016/j.jpowsour.2015.02.116, 283, 320-327, 2015.06, [URL], Mg/Al-hydrotalcite (HDT)-dispersed paper-structured catalyst (PSC) was prepared by a simple paper-making process. The PSC exhibited excellent catalytic activity for the steam reforming of model biodiesel fuel (BDF), pure oleic acid methyl ester (oleic-FAME, C19H36O2) which is a mono-unsaturated component of practical BDFs. The PSC exhibited fuel conversion comparable to a pelletized catalyst material, here, conventional Ni-zirconia cermet anode for solid oxide fuel cell (SOFC) with less than one-hundredth Ni weight. Performance of electrolyte-supported cell connected with the PSC was evaluated in the feed of oleic-FAME, and stable operation was achieved. After 60 h test, coking was not observed in both SOFC anode and PSC..
177. Liang ZHAO, Nicola H. PERRY, Takeshi DAIO, Kazunari SASAKI, Sean R. BISHOP, Improving the Si Impurity Tolerance of Pr0.1Ce0.9O2-delta SOFC Electrodes with Reactive Surface Additives, Chem. Mater. , 10.1021/acs.chemmater.5b00501, 27, 8, 3065-3070, 2015.04.
178. TRAN Quang Tuyen, Taku KAIDA, Mio SAKAMOTO, Kazunari SASAKI, Yusuke SHIRATORI, Effectiveness of paper-structured catalyst for the operation of biodiesel-fueled solid oxide fuel cell, J. Power Sources, 283, 320-327, 2015.02.
179. Makito Okumura, Yohei Nagamatsu, Zhiyun Noda, Yuya Tachikawa, Takeshi Daio, Akari Hayashi, Kazunari Sasaki, A FIB-SEM study on correlations between PEFC electrocatalyst microstructure and cell performance, Symposium on Polymer Electrolyte Fuel Cells 15, PEFC 2015 - 228th ECS Meeting
Polymer Electrolyte Fuel Cells 15, PEFC 15
, 10.1149/06917.0709ecst, 709-714, 2015.01, [URL], PEFC electrocatalyst microstructure strongly influences cell performance. In this study, Nafion ionomer content in the cathode electrocatalyst layer is systematically varied to modify the electrocatalyst microstructure. Current-voltage characteristics of the membrane-electrode-assemblies are measured and then the electrocatalyst microstructure is observed by the focused-ion-beam coupled scanning electron microscopy (FIB-SEM) to examine the correlations between the 3D microstructure and the cell performance. Although technical limitation was found for FIBSEM analysis, certain correlations were also established..
180. Y. Matsuzaki, Y. Tachikawa, T. Hatae, H. Matsumoto, S. Taniguchi, K. Sasaki, A parametric study of SOFC performances with multi-stage electrochemical oxidation for enhancement of electric efficiency, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1961ecst, 1961-1968, 2015.01, [URL], The solid-state ceramic construction of SOFCs enables high fuel to electricity conversion efficiencies of as high as 50 to 60 percent LHV in high temperature operation, and allows more flexibility in fuel choice. In this study, we have developed a symbolic analysis method to investigate the availability of variable parameters appearing in multi-stage electrochemical oxidation mechanism that is expected to further improve the electric efficiencies of SOFCs. In the flow system of the multi-stage oxidation, the fuel utilization, Uf, at the most downstream stack, UfM, is expressed as a function of number of stacks, n, and total fuel utilization, UfT. When n = 10 and UfT = 85%, UfM is calculated to be 36%, which is much smaller than UfT. Therefore, if the most downstream stack has high robustness against lean fuel gas, UfT could be set to higher values without serious degradation by using this flow system..
181. X. Shen, K. Sasaki, Development of robust SOFC anode materials using la-doped SrTiO3, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1447ecst, 1447-1453, 2015.01, [URL], We utilized stable Sr0.9La0.1TiO3 (SLT) with Ce0.9Gd0.1O2 (GDC) and (Sc2O3)0.1(CeO2)0.01(ZrO2)0.89 (SSZ) to fabricate robust anode for SSZ electrolyte-supported SOFC single cell. The anode consisted of three layers: a layer of 60wt% GDC-SLT or 40wt% SSZ-SLT as a functional layer and two layers of SLT as current conducting layers. Cathode was composed of a layer of 50wt% SSZ-LSM as a functional layer and a layer of LSM as a current conducting layer. Impregnation method has been employed to decorate nano-sized Ni and CeO2 into the ceramic anode. We measured electrochemical properties of single cells in 3%-humidified H2 at 800°C, and investigated long-term redox stability of the nano-sized catalyst impregnated ceramic anodes by fuel interruption method..
182. T. Hatae, K. Sato, T. Somekawa, Y. Matsuzaki, S. Amaha, M. Yoshikawa, Y. Mugikura, K. Miyara, T. Oshima, S. Taniguchi, K. Sasaki, M. Shimazu, Y. Takahashi, A. Kawakami, N. Mori, H. Yokokawa, Durability assessment of SOFC stacks with several types of structures for thermal cycles during their lifetimes on residential use, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.2209ecst, 2209-2216, 2015.01, [URL], We have been developing a rapid evaluation method for durability of SOFC stacks for thermal cycles during their lifetimes based on the assumption of residential use. The durability for thermal cycles is expected to be affected by the degradation during their long-term operation. In order to accelerate the evaluation, treatments to intentionally cause degradation were investigated. A degradation factor was determined depending on the SOFC stacks with different structures respectively because each degradation mechanism during their long-term operation also depends on them. The SOFC stacks were supplied by four SOFC stack manufactures in Japan. In this work, we investigated the Cr poisoning treatment to tubular SOFC (TOTO) and the S poisoning treatment to singlestep co-fired planar SOFC (Murata Manufacturing). As results of both cases, 10 years' worth of degradation was successful to be intentionally caused in short period..
183. H. C. Pham, S. Taniguchi, Y. Inoue, J. T. Chou, T. Izumi, K. Matsuoka, K. Sasaki, Electrical and oxidation resistance of surface oxide of porous Fe-Cr-Al alloy for the application of metal supported SOFCs, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1715ecst, 1715-1720, 2015.01, [URL], We have investigated the property of Fe-Cr-Al-type stainless steel as a porous alloy substrate for metal-supported SOFCs especially on the cathode side. We confirmed not only good heat resistance but also low electrical resistance at the interface between the porous substrate and a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) coating at 700°C in air. Long-term durability of the oxidation resistance of the LSCF-coated Fe-Cr-Al alloy at 700°C was investigated by measuring the mass gain, surface oxide thickness, and electrical resistance at different temperatures from 700 to 900°C..
184. L. Zhao, N. H. Perry, K. Sasaki, S. R. Bishop, Enhancement of surface oxygen exchange kinetics for Pr0.1Ce0.9O2-δ with deposition of La or Sm oxide, 1st Symposium on Solid-Gas Electrochemical Interfaces, SGEI 2015 - 227th ECS Meeting
Solid-Gas Electrochemical Interfaces � SGEI 1
, 10.1149/06602.0157ecst, 157-160, 2015.01, [URL], Rapid oxygen transport across the gas/solid interface (oxygen exchange) is critical for solid oxide fuel cell electrode performance. In this work, La and Sm are shown to dramatically improve the oxygen exchange rate on Pr0.1Ce0.9O2-δ thin films (>50 x at 450 °C) as compared to a freshly deposited film without La or Sm oxide. A surface cleaning effect from the La and Sm is suspected as the source of the enhancement, though catalytic activity from La and Sm may also play a role..
185. T. Hosoi, T. Yonekura, K. Sunada, K. Sasaki, Exchange current density of SOFC electrodes
Theoretical relations and partial pressure dependencies rate-determined by electrochemical reactions, Journal of the Electrochemical Society, 10.1149/2.0561501jes, 162, 1, F136-F152, 2015.01, [URL], As a theoretical consideration on electrode defect chemistry, general relations of exchange current density quantitatively representing Solid Oxide Fuel Cell (SOFC) electrode performance are systematically derived as a function of gas partial pressures, equilibrium constants of adsorption and dissociation reactions on electrode surfaces, and electrochemical reaction rate constants for possible elemental reactions at the cathode and the anode, in the case that an electrochemical reaction is the rate-determining electrode reaction. Simplified expressions are also derived, under the condition that one kind of neutral or charged adsorbed species is predominant at the electrode, to derive gas partial pressure dependence of exchange current density for given rate-determining electrochemical reactions. Importance of considering elementary steps is highlighted to derive rate equations and to clarify various dependencies. Partial pressure dependencies of the exchange current density are compiled and discussed by simulating normalized exchange current density values for given partial pressures. The applicability and limitation of the Butler-Volmer type expressions of exchange current density for SOFC electrodes are carefully discussed..
186. Y. Tachikawa, J. Sugimoto, M. Takada, T. Kawabata, S. M. Lyth, Y. Shiratori, K. Sasaki, In operando visualization of SOFC electrodes by thermography and visible light imaging, ECS Electrochemistry Letters, 10.1149/2.0031511eel, 4, 11, F61-F64, 2015.01, [URL], The temperature distribution in internal reforming SOFC anodes can be visualized by thermography. However, thermal imaging techniques are limited since they cannot take into account the influence of emissivity changes caused by carbon deposition on the anode. This problem can be solved by simultaneous visualization using thermography and visible light imaging. By combining these techniques, carbon deposition can be monitored via visible light imaging, whilst temperature changes due to the reforming reaction can be monitored by thermal imaging. This in operando visualization technique enables the evaluation and prediction of the distribution of multiple chemical reactions on the SOFC electrodes..
187. Daiki Ishibashi, Eunjoo Park, Shunsuke Taniguchi, Yuko Inoue, Jyh Tyng Chou, Kazunari Sasaki, Influence of cathode polarization change on chromium deposited on electrolyte surface near cathode reaction sites of SOFC, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1031ecst, 1031-1037, 2015.01, [URL], It has been clarified that Cr deposition occurs significantly on the electrolyte surface near cathode reaction sites as a consequence of cathode polarization. In this study, we investigated the influence of a change in the cathode polarization on the Cr deposited on the electrolyte surface by using NiO/YSZ or NiO/GDC as the cathode material. The deposited Cr segregated at the interface of NiO and YSZ in the case of the NiO/YSZ cathode after a decrease in the cathode polarization, which suggests nucleation under a cathode polarization of 200 mV and growth of Cr compounds after decreasing the cathode polarization. In contrast, the amount of deposited Cr decreased in the case of the NiO/GDC cathode after decreasing the cathode polarization..
188. Masahiko Kitamura, Zhiyun Noda, Junko Matsuda, Akari Hayashi, Kazunari Sasaki, Investigation of durability of MEAs at higher temperature, Symposium on Polymer Electrolyte Fuel Cells 15, PEFC 2015 - 228th ECS Meeting
Polymer Electrolyte Fuel Cells 15, PEFC 15
, 10.1149/06917.0701ecst, 701-708, 2015.01, [URL], For the next generation polymer electrolyte fuel cell (PEFC), increase in operating temperature above 100 °C is desired in order to improve the cathode overvoltage. The objective of this study is to understand degradation phenomena of cathode catalysts by simulating fuel cell vehicle-s "load cycles", where Pt dissolution/reprecipitation reaction occurs. Standard membrane-electrode-assemblies (MEAs) made with Nafion® membrane were evaluated under increased temperature like 105 °C and also under reduced humidity condition like RH57%. As a result, comparing to the standard operating condition (80 °C and RH100%), Pt enlargement was suppressed at RH57% owing to the presence of smaller amount of water. However, degradation of Nafion® ionomer under low humidity condition led to lowering MEA performance. Furthermore, at higher temperature, in addition to Nafion® degradation, enhanced Pt enlargement was recognized and became a serious problem on MEA performance..
189. S. Kanae, Y. Toyofuku, T. Kawabata, Y. Inoue, T. Daio, J. Matsuda, J. T. Chou, Y. Shiratori, S. Taniguchi, K. Sasaki, Microstructural characterization of SrZrO3 formation and the influence to SOFC performance, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.2463ecst, 2463-2470, 2015.01, [URL], One of the major phenomena to shorten SOFC durability is the formation of insulating phases, such as SrZrO3, between the cathode and the electrolyte. It is known that SrZrO3 is formed and grown during sintering processes as well as during long-term operation. A systematic study is made to examine the SrZrO3 formation mechanisms and their influence on electrochemical properties..
190. T. Kawasaki, J. Sugimoto, Y. Tachikawa, Y. Shiratori, S. Taniguchi, K. Sasaki, Oxidation-induced degradation of SOFC Ni anodes at high fuel utilizations, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1345ecst, 1345-1352, 2015.01, [URL], In the downstream of SOFC systems, higher oxygen partial pressure can cause oxidation-induced Ni anode degradation. In this study, we have investigated cell performance at high fuel utilizations for simulating situations around the system downstream. When the anode voltage was higher than a voltage threshold, the cell performance was stable. On the other hand, it became unstable associated with cell voltage oscillation when anode voltage was around or less than the threshold value. The threshold value was consistent with the anode potential derived from the oxygen partial pressure at the phase boundary at which both Ni and NiO coexist..
191. Y. Tachikawa, Y. Matsuzaki, T. Hatae, S. Taniguchi, K. Sasaki, Process analysis for achieving highly enhanced total efficiency on multi-stage fuel supplied SOFC system, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.3107ecst, 3107-3113, 2015.01, [URL], A multi-stage fuel supply SOFC system is studied, which has additional fuel supply inlets between each SOFC stack. The anode offgas from the first stack is supplied to the next stack as reformed fuel gas being mixed with additional fresh fuel. In this paper, the effect of the additional fuel flow ratio is evaluated. The electric efficiency and the fuel utilization of the system can be improved in applying multi-stage fuel supply design..
192. Masahiro Iwami, Dai Horiguchi, Zhiyun Noda, Akari Hayashi, Kazunari Sasaki, Pt-decorated TiO2 electrocatalysts for PEFCs, Symposium on Polymer Electrolyte Fuel Cells 15, PEFC 2015 - 228th ECS Meeting
Polymer Electrolyte Fuel Cells 15, PEFC 15
, 10.1149/06917.0603ecst, 603-609, 2015.01, [URL], For polymer electrolyte fuel cell (PEFC) electrocatalysts, carbon corrosion is one of the important technological issues to be solved. TiO2 is a possible alternative support material. In this study, vaporgrown carbon fiber (VGCF-H) conductive fillers are applied as the built-in electron-conductive backbone, on which Nb-doped TiO2 is coated and Pt nanoparticles are then impregnated. FESEM images of Pt/Ti0.95Nb0.05O2/VGCF-H reveal selective impregnation of Pt nanoparticles on the TiO2 grains rather than the VGCF-H conductive fillers. This conductive-filler-integrated electrocatalyst exhibits relatively higher electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity, compared to the electrocatalysts without conductive fillers..
193. K. Sasaki, S. Taniguchi, Y. Shiratori, A. Hayashi, T. Oshima, M. Nishihara, Y. Tachikawa, T. Daio, T. Kawabata, M. Fujita, A. Zaitsu, Smart fuel cell demonstration project
A challenge to realize SOFC-powered campus, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.0171ecst, 171-178, 2015.01, [URL], This paper introduces a challenge to realize a fuel-cell-powered campus at Kyushu University where SOFC technology plays a major role. The Smart Fuel Cell Demonstration Project, supported by Cabinet Secretariat/Office of Japan, enables us to install one 250 kW SOFC power generation system, other SOFC units, and the world-first university-owned fuel cell vehicle to which renewable hydrogen gas is supplied from the hydrogen refueling station on the campus using electrolyzers. The experience in this demonstrative project is described along with related efforts to accelerate industry-academia collaborations and fundamental scientific studies using advanced analytical facilities..
194. Wen Ma, Jae Jin Kim, Nikolai Tsvetkov, Takeshi Daio, Yener Kuru, Zhuhua Cai, Yan Chen, Kazunari Sasaki, Harry L. Tuller, Bilge Yildiz, Vertically aligned nanocomposite La0.8Sr0.2CoO3/(La0.5Sr0.5)2CoO4 cathodes-electronic structure, surface chemistry and oxygen reduction kinetics, Journal of Materials Chemistry A, 10.1039/c4ta04993d, 3, 1, 207-219, 2015.01, [URL], The hetero-interfaces between the perovskite (La1-xSrx)CoO3 (LSC113) and the Ruddlesden-Popper (La1-xSrx)2CoO4 (LSC214) phases have recently been reported to exhibit fast oxygen exchange kinetics. Vertically aligned nanocomposite (VAN) structures offer the potential for embedding a high density of such special interfaces in the cathode of a solid oxide fuel cell in a controllable and optimized manner. In this work, VAN thin films with hetero-epitaxial interfaces between LSC113 and LSC214 were prepared by pulsed laser deposition. In situ scanning tunneling spectroscopy established that the LSC214 domains in the VAN structure became electronically activated, by charge transfer across interfaces with adjacent LSC113 domains above 250 °C in 10-3 mbar of oxygen gas. Atomic force microscopy and X-ray photoelectron spectroscopy analysis revealed that interfacing LSC214 with LSC113 also provides for a more stable cation chemistry at the surface of LSC214 within the VAN structure, as compared to single phase LSC214 films. Oxygen reduction kinetics on the VAN cathode was found to exhibit approximately a 10-fold enhancement compared to either single phase LSC113 and LSC214 in the temperature range of 320-400°C. The higher reactivity of the VAN surface to the oxygen reduction reaction is attributed to enhanced electron availability for charge transfer and the suppression of detrimental cation segregation. The instability of the LSC113/214 hetero-structure surface chemistry at temperatures above 400°C, however, was found to lead to degraded ORR kinetics. Thus, while VAN structures hold great promise for offering highly ORR reactive electrodes, efforts towards the identification of more stable hetero-structure compositions for high temperature functionality are warranted. This journal is.
195. Y. Tachikawa, T. Kawabata, Y. Shiratori, K. Sasaki, Visualization of SOFC anode by dual imaging method using infrared and visible light cameras, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015
, 10.1149/06801.1115ecst, 1115-1120, 2015.01, [URL], Thermography imaging can be applied for the surface of an SOFC electrode to evaluate the spatial distribution of reforming and electrode reactions. For getting a correct temperature distribution by thermography, emissivity change on the object surface caused by chemical reactions or material coverage must be precisely evaluated. In-situ observation using both infrared and visible light dual cameras enables us to obtain precise emissivity change and thus temperature distribution, because the influence of emissivity change can be corrected by the visible light imaging technique. In this study, this imaging method is applied for an anode material which was exposed to a fuel flow causing coke formation, and the information on the carbon distribution was successfully separated on the anode surface to obtain the true temperature distribution..
196. 水谷千晶, 北原 辰巳, 中島 裕典, 佐々木 一成, 伊藤 衡平, 極細熱電対群を用いたPEFC 内部の3 次元温度分布計測と水挙動の解析, 日本機械学会論文集, 80, 820, No. 14-00277, 2014.12.
197. Takami HOSOI, Takahiro YONEKURA, Kyohei SUNADA, Kazunari SASAKI, Exchange Current Density of SOFC Electrodes: Theoretical Relations and Partial Pressure Dependencies 10 Rate-Determined by Electrochemical Reactions, J. Electrochem. Soc., 162, 1, F136-F152, 2014.12.
198. T. Bayer, S. R. Bishop, M. Nishihara, K. Sasaki, S. M. Lyth, Characterization of a graphene oxide membrane fuel cell, Journal of Power Sources, 10.1016/j.jpowsour.2014.08.071, 272, 239-247, 2014.12, [URL], The electrical, mechanical, and compositional characterization of a graphene oxide membrane is presented, and its application as an electrolyte material in a polymer electrolyte membrane fuel cell is explored. Self-supporting graphene oxide membranes were prepared by a simple vacuum filtration process and, for the first time, characterized as the electrolyte in a fuel cell operating in an elevated temperature range (30-80 °C), with a maximum power density of ∼34 mW cm-2, approaching that of a Nafion electrolyte based cell prepared and tested under similar conditions. Evidence for partial membrane reduction was found at higher temperatures and is believed to originate from more easily released, higher energy oxide groups, such as epoxides. We also discuss the morphology, the mechanical properties, chemical composition, and electrical conductivity of the graphene oxide membranes, with comparisons made to conventional Nafion membranes..
199. Y. Kobayashi, K. Kosaka, K. Tomida, N. Matake, K. Ito, K. Sasaki, Start-up characteristics of segmented-in-series tubular SOFC power modules improved by catalytic combustion at cathodes, Fuel Cells, 10.1002/fuce.201400014, 14, 6, 1028-1035, 2014.12, [URL], For large-scale SOFC power generation systems, a shorter start-up time of SOFC cell stacks with relatively large heat capacity is one of the most important technological issues to determine the flexibility in SOFC system operation. In this study, start-up procedures have been examined to shorten the start-up time period. The conventional heating procedure using pre-heated hot air and self-heating by SOFC operation at low temperatures had a difficulty to shorten the start-up time period because of the limitation in power generation at lower temperatures. In this study, as an alternative start-up procedure, catalytic combustion at the SOFC cathodes is, for the first time, demonstrated to be useful on the system level. The applicability of the catalytic combustion to shorten the start-up time period has been verified numerically as well as experimentally by using a large-scale cell stack cartridge. This unique start-up procedure enables to operate SOFC-based large-scale power generation systems..
200. Wen MA, Jae Jin KIM, Nikolai TSVETKOV, Takeshi DAIO, Yener KURU, Zhuhua CAI, Yan CHEN, Kazunari SASAKI, Harry L. TULLER, Bilge YILDIZ, Vertically Aligned Nanocomposite La0.8Sr0.2CoO3/(La0.5Sr0.5)2CoO4 Cathodes - Electronic Structure, Surface Chemistry and Oxygen Reduction Kinetics, J. Mater. Chem. A, 3, 207-219, 2014.10.
201. Yohei NAGAMATSU, Kohei KANDA, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Electrochemical Performance of MEAs with Pt/SnO2 Mixed with Conductive Fillers, ECS Transactions, 64, 3, 207-213, 2014.10.
202. Dai HORIGUCHI, Takuya TSUKATSUNE, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Pt/SnO2 Electrocatalysts on Conductive Fillers, ECS Transactions, 64, 3, 215-220, 2014.10.
203. Jianfeng LIU, Takeshi DAIO, Stephen M. LYTH, Kazunari SASAKI, Defective Nitrogen-Doped Graphene Foam: Clarifying the Role of Nitrogen in Non-Precious ORR Catalysts, ECS Transactions, 64, 3, 271-280, 2014.10.
204. Thomas BAYER, Sean R. BISHOP, Masamichi NISHIHARA, Kazunari SASAKI, Stephen M. LYTH, Graphene Oxide Membrane Fuel Cells: Utilizing of a New Class of Ionic Conductor, ECS Transactions, 64, 3, 441-448, 2014.10.
205. Masahiko KITAMURA, Yasuto MINAMIDA, Xiaojing ZHAO, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Investigation of Performance and Durability of MEAs at Higher Temperature, ECS Transactions, 64, 3, 755-762, 2014.10.
206. Jianfeng LIU, Kazunari SASAKI, Stephen M. LYTH, Defective Nitrogen-Doped Graphene Foam: A Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Medium, ECS Transactions, 64, 3, 1161-1172, 2014.10.
207. Yasuto MINAMIDA, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Development of MEAs with Pt/Mesoporous Carbon as a Cathode Catalyst, ECS Transactions, 64, 3, 137-144, 2014.10.
208. Kazunari SASAKI, Zhiyun NODA, Takuya TSUKATSUNE, Kohei KANDA, Yuma TAKABATAKE, Yohei NAGAMATSU, Takeshi DAIO, Stephen M. LYTH, Akari HAYASHI, Alternative Oxide-supported PEFC Electrocatalysts, ECS Transactions, 64, 3, 221-227, 2014.10.
209. Yoshinori Kobayashi, Kenichiro Kosaka, Takashi Yamamoto, Yuya Tachikawa, Kohei Ito, Kazunari Sasaki, A solid polymer water electrolysis system utilizing natural circulation, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2014.07.153, 39, 29, 16263-16274, 2014.10, [URL], Solid Polymer Water Electrolysis (SPWE) is a method to efficiently produce high-purity hydrogen gas using a polymer electrolyte membrane-based system. SPWE systems that utilize natural water circulation (resulting from a difference in buoyancy) are a promising technology, which need no additional circulation pump for water supply to the electrolysis cells, and generate no pressure difference between the hydrogen generation and oxygen generation chambers. However, despite not needing an accurate pressure control, gas bubbles formed and trapped within the cell stacks can inhibit heat convection, leading to hot-spot formation and consequent destructive degradation. Improving the reliability is therefore one of the most important technological issues in natural circulation SPWEs. In this study, hot-spot formation is studied both by numerical heat and flow analysis, and by experimental in-situ visualization. This leads to insights into the degradation mechanisms of SPWE stacks, and their possible solutions. An improved design for an SPWE cell stack is successfully fabricated, and reliable operation up to 5000 h is demonstrated..
210. L. Zhao, N. H. Perry, K. Sasaki, S. R. Bishop, Electronic and ionic conductivity of Eu0.2Ce0.8O 2-δ, Solid State Ionics, 10.1016/j.ssi.2014.05.010, 263, 75-79, 2014.10, [URL], Eu-doped cerium oxide was synthesized and its crystal structure was analyzed by X-ray diffraction. The electrical conductivity was measured by impedance spectroscopy at 350-900 °C over a wide range of controlled oxygen partial pressures, from H2 to O2, using gas mixtures. In the high pO2 region, ionic conductivity is predominant, and the activation energy for total conductivity is 0.8 ± 0.01 eV. In low pO 2, the conductivity is found to obey a - 1/4 power law dependence on pO2, with an enthalpy of reduction of 4.2 ± 0.16 eV. These results demonstrate that Eu has a similar effect on electrical properties as Gd or Sm acceptor dopants in ceria, namely, that Eu shows no evidence for multivalent behavior; rather, it appears to be a fixed valent dopant in the fluorite structured ceria, in contrast to prior studies finding multivalency of Eu in perovskite oxides under similar conditions..
211. Liana Christiani, Sandra Hilaire, Kazunari Sasaki, Masamichi Nishihara, Evaluation of proton conductivity of sulfonated polyimide/dihydroxy naphthalene charge-transfer complex hybrid membranes, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.27343, 52, 20, 2991-2997, 2014.10, [URL], Sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) charge-transfer (CT) complex hybrid films were investigated as possible alternative for polymer electrolyte membranes in polymer electrolyte fuel cells. SPI/DHN CT complex hybrid films include CT complexes, which might work as electronic conductors, and sulfonic acid units, which could work as proton conductors. Therefore, the origin of the conductivity of SPI/DHN complex hybrid films was evaluated by four-probe impedance measurements in the through-plane direction of the films. The obtained conductivity of the CT complex hybrid films increased with the increase of ion exchange capacity of the CT films and the decrease of CT complex concentration in the films. These results indicated that proton transfer dominantly occurred in the CT complex hybrid films. Proton conductivity of the CT complex hybrid films consisting of 2,6- or 1,5-DHN showed the similar values, although the molecular geometries of the CT complex were different. The activation energy values for proton conductivity in the CT films were approximately the same as that of Nafion 212. Water uptake (WU) results were also conducted and suggest that CT complex formation could control the degree of WU of the films and prevent dissolution of SPI..
212. J. Liu, D. Takeshi, K. Sasaki, S. M. Lyth, Platinum-Decorated Nitrogen-Doped Graphene Foam Electrocatalysts, Fuel Cells, 10.1002/fuce.201300258, 14, 5, 728-734, 2014.10, [URL], Large-scale, facile synthesis of nitrogen-doped graphene foam (GF) from low cost precursors is reported as a support material for platinum in fuel cell cathodes. The nitrogen-doped GF was produced by combustion of nitrogen-containing sodium alkoxide, followed by washing and heat treatment in various gases. A nitrogen-free reference sample was also synthesized. The BET surface area is higher than 700 m2 g-1, and the material is highly defective, partly due to the inclusion of nitrogen, and partly due to the low temperature, catalyst-free synthesis method. These defects result in an excellent distribution of platinum nanoparticles on the surface. The electrochemical performance of the resulting electrocatalysts was characterized using cyclic voltammetry and linear sweep voltammetry, revealing that nitrogen doping has potential to increase the durability of graphene-based catalysts. Therefore, this material is a potentially useful catalyst support for use in polymer electrolyte membrane fuel cells..
213. Yoshinori KOBAYASHI, Kenichiro KOSAKA, Kazuo TOMIDA, Norihisa MATAKE, Kohei ITO, Kazunari SASAKI, Start-Up Characteristics of Segmented-In-Series Tubular SOFC Power Modules Improved by Catalytic Combustion at Cathodes, Fuel Cell, 14, 1028-1035, 2014.09.
214. Eunjoo Park, Shunsuke Taniguchi, Takeshi Daio, Jyh Tyng Chou, Kazunari Sasaki, Comparison of chromium poisoning among solid oxide fuel cell cathode materials, Solid State Ionics, 10.1016/j.ssi.2014.01.047, 262, 421-427, 2014.09, [URL], Chromium poisoning phenomena of solid oxide fuel cells (SOFCs) were investigated using (La0.8Sr0.2)0.98MnO 3 (LSM), Pr0.8Sr0.2MnO3 (PrSM), Nd0.8Sr0.2MnO3 (NdSM), and Br 0.5Sr0.5Co0.8Fe0.2O3 (BSCF) for the cathode materials and yttria-stabilized zirconia (YSZ) as the electrolyte material at 700 °C under constant cathode polarization conditions. Deposition of chromium increased with increasing cathode polarization similarly for the four cathodes, although position of the deposition was different for the BSCF cathode. Chromium deposited near the cathode/electrolyte interface for the LSM cathode, the PrSM cathode and the NdSM cathode. Chromium deposition on the surface of the zirconia electrolyte was observed for the PrSM cathode and the NdSM cathode as previously observed in the LSM cathode. Oxygen deficiency in the deposited chromium on the surface of the zirconia electrolyte was also observed, thus the reaction mechanism of chromium vapor with the oxygen vacancy induced by cathode polarization was supported. The oxygen vacancy on the surface of the zirconia electrolyte seemed to be generated via metal oxides such as manganese oxide or neodymium oxide segregated from the cathode materials. Chromium deposited on the surface of the BSCF cathode. Cathode polarization seems to increase reactivity of BSCF and enhance trapping of chromium vapor near the cathode surface..
215. M. Hanasaki, C. Uryu, T. Daio, T. Kawabata, Y. Tachikawa, S. M. Lyth, Y. Shiratori, S. Taniguchi, K. Sasaki, SOFC durability against standby and shutdown cycling, Journal of the Electrochemical Society, 10.1149/2.0421409jes, 161, 9, F850-F860, 2014.09, [URL], To simulate realistic operating conditions in SOFC systems, we investigate the influence of thermal cycling on the performance of electrolyte-supported planar SOFCs. Thermal cycling is often associated with interruption of fuel supply, with three main modes; hot standby, cold standby, and shutdown. Cell performance degradation is most significant during shutdown cycles. Nickel oxidation and agglomeration are more pronounced when SOFCs are subjected to lower temperatures for longer periods of time, leading to significant performance degradation. Ostwald ripening at the anode leads to degradation as Ni grains increase in size with cycling. Ni particle precipitation on the anode zirconia grains and along electrolyte grain boundaries is found for the first time in shutdown cycling tests. When H2S is mixed with the fuel, the internal reforming reactions and electrode reactions are inhibited by sulfur poisoning of the Ni anodes, accelerating degradation. The SOFC cycling degradation mechanisms are discussed in detail..
216. Liana CHRISTIANI, Sandra HILAIRE, Kazunari SASAKI, Masamichi NISHIHARA, Evaluation Of Proton Conductivity Of Sulfonated Polyimide/Dihydroxy Naphthalene Charge-Transfer Complex Hybrid Membranes, J. Polym. Sci. A, 52, 20, 2991-2997, 2014.08.
217. Takuya TSUKATSUNE, Yuma TAKABATAKE, Zhiyun NODA, Takeshi DAIO, Ayumi ZAITSU, Stephen M. LYTH, Akari HAYASHI, Kazunari SASAKI, Platinum-Decorated Tin Oxide and Niobium-Doped Tin Oxide PEFC Electrocatalysts: Oxygen Reduction Reaction Activity, J. Electrochem. Soc., 161, 12, F1208-F1213, 2014.08.
218. Thomas BAYER, Sean R. BISHOP, Masamichi NISHIHARA, Kazunari SASAKI, Stephen M. LYTH, Characterization of a Graphene Oxide Membrane Fuel Cell, J. Power Sources, 272, 239-247, 2014.08.
219. Sean R. BISHOP, Liang ZHAO, Takeshi DAIO, Nicola H. PERRY, Kazunari SASAKI, Oxygen Exchange Kineics of Thin Films Studied by Optical Transmission Relaxation: Correlation with Surface Composition and Microstructure, Microscopy and Microanalysis, 20, S3, 1906-1907, 2014.08.
220. Yoshinori KOBAYASHI, Kenichiro KOSAKA, Takashi YAMAMOTO, Yuya TACHIKAWA, Kohei ITO, Kazunari SASAKI, A Solid Polymer Water Electrolysis System Utilizing Natural Circulation, Intl. J. of Hydrogen Energy, 39, 16263-16274, 2014.08.
221. Jianfeng LIU, Takeshi DAIO, Kazunari SASAKI, Stephen M. LYTH, Platinum-Decorated Nitrogen-Doped Graphene Foam Electrocatalysts, FUEL CELLS, 14, 5, 728-734, 2014.08.
222. S. R. Bishop, L. Zhao, T. Daio, N. Perry, K. Sasaki, Oxygen exchange kineics of thin ftilms studied by optical transmission relaxation
Correlation with surface composition and microstructure, Microscopy and Microanalysis 2014, M and M 2014
Microscopy and Microanalysis
, 10.1017/S143192761401126X, 20, 3, 1906-1907, 2014.08, [URL].
223. Liang ZHAO, Nicola H. PERRY, Kazunari SASAKI, Sean R. BISHOP, Electronic and ionic conductivity of Eu0.2Ce0.8O2 - δ, Solid State Ionics, 263, 75-79, 2014.06.
224. Jianfeng LIU, Takeshi DAIO, Kazunari SASAKI, Stephen M. LYTH, Defective Graphene Foam: A Platinum Catalyst Support for PEMFCs, J.Electrochem.Soc., 161, 9, F838-F844, 2014.05.
225. Y. Takabatake, Z. Noda, S. M. Lyth, A. Hayashi, K. Sasaki, Cycle durability of metal oxide supports for PEFC electrocatalysts, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2014.01.094, 39, 10, 5074-5082, 2014.03, [URL], In order to develop durable electrocatalysts for polymer electrolyte fuel cells, six different metal oxides, namely MoO3, SnO2, Nb2O5, Ta2O5, TiO2, and WO3, are selected as thermochemically stable, carbon-free platinum electrocatalyst support materials. The stability of Pt on these alternative oxide support materials is systematically analyzed, for the first time, using common experimental protocols simulating realistic fuel cell vehicle operation. Pt/SnO2 shows the best performance in terms of both electrochemical activity, and stability against dissolution. Pt dissolution rates in Pt/SnO 2 are comparable to those of conventional Pt/C electrocatalysts. These results suggest that SnO2 is a promising candidate as an alternative electrocatalyst support..
226. Kohei KANDA, Zhyun NODA, Yohei NAGAMATSU, Takahiro HIGASHI, Shunsuke TANIGUCHI, Stephen Matthew LYTH, Akari HAYASHI, Kazunari SASAKI, Negligible Start-Stop-Cycle Degradation in a PEFC Utilizing Platinum-Decorated Tin Oxide Electrocatalyst Layers with Carbon Fiber Filler., ECS Electrochemistry Letters, 3, 4, F15-F18, 2014.02.
227. Jianfeng LIU, Takeshi DAIO, Daniel OREJON, Kazunari SASAKI, Stephen Matthew LYTH, Defective Nitrogen-Doped Graphene Foam: A Metal-Free, Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Acid., J. Electrochem. Soc., 161, 4, F544-F550, 2014.02.
228. Eunjoo PARK, Shunsuke TANIGUCHI, Takeshi DAIO, Jyh-Tyng CHOU, Kazunari SASAKI, Comparison of chromium poisoning among solid oxide fuel cell cathode materials, Solid State Ionics, 262, 421-427, 2014.02.
229. Masamichi Nishihara, Liana Christiani, Aleksandar Staykov, Kazunari Sasaki, Experimental and theoretical study of charge-transfer complex hybrid polyimide membranes, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.23411, 52, 4, 293-298, 2014.02, [URL], The nanostructure of sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer (CT) complex hybrid films, which are noble alternative polymer electrolyte membranes (PEMs), is determined by a combined visible spectroscopy/quantum mechanical approach. From the visible spectra of SPI/2,6-dihydroxynaphthalene (2,6-DHN) and 1,5-dihydroxynaphthalene (1,5-DHN) CT complex hybrid films, it is confirmed that these films have different maximum wavelength, although difference of the molecular structure is small. From the calculation based on the experimental result, SPI and DHNs form multiple interactions consisting of not only CT interaction, but also hydrogen bonding in multilayered structures. CT interaction between SPI and DHN defines the DHN position in the SPI matrix, with DHN sitting in the cavity formed between SPIs. The molecular structure of the CT films derived from the multiple and complex interactions can recognize small differences in the structural isomers and bring changes of the optical property. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 293-298 Many sulfonated polyimides (SPIs) have been actively investigated as polymer electrolyte membranes (PEMs) for polymer electrolyte fuel cells (PEFCs) as alternatives to Nafion. In this work, the molecular geometry of (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer complex hybrid films is determined by a combined visible spectroscopy/quantum mechanical approach. From the experimental and calculated results for SPI/2,6-DHN and 1,5-DHN, while the structural difference is small, different molecular geometries and optical properties can be seen..
230. Eunjoo PARK, Shunsuke TANIGUCHI, Takeshi DAIO, Jyh-Tyng CHOU, Kazunari SASAKI, Influence of Cathode Polarization on the Chromium Deposition near the Cathode/Electrolyte Interface of SOFC.
, Intl. J. Hydrogen Energy, 39, 3, 1463-1475, 2014.01.
231. K. Sasaki, Z. Noda, T. Tsukatsune, K. Kanda, Y. Takabatake, Y. Nagamatsu, T. Daio, S. M. Lyth, A. Hayashi, Alternative oxide-supported PEFC electrocatalysts, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0221ecst, 221-227, 2014.01, [URL], Possible alternative electrocatalyst support materials to the conventional carbon black have been examined. Among others, doped-SnO2 can be a promising support for Pt nanoparticles well connected to the oxide with a certain crystallographic orientation. Pt/doped SnO2 exhibits suitable voltage cycle durability, while further improvement in oxygen reduction reaction (ORR) activity is still desired..
232. J. Liu, K. Sasaki, S. M. Lyth, Defective nitrogen-doped graphene foam
A non-precious electrocatalyst for the oxygen reduction reaction in alkaline medium, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.1161ecst, 1161-1172, 2014.01, [URL], The oxygen reduction reaction has faster kinetics in anion exchange membrane fuel cell, opening the possibility of using nonprecious materials as electrocatalysts. Therefore, defective nitrogen-doped graphene foam is applied as an electrocatalyst in alkaline medium. The large surface area and highly porous structure results in high oxygen reduction reaction activity in rotating ring-disk electrode measurements. During potential cycling tests, the nitrogen-doped graphene foam displayed comparable durability to a Pt/CB catalyst..
233. J. Liu, T. Daio, K. Sasaki, S. M. Lyth, Defective nitrogen-doped graphene foam
Clarifying the role of nitrogen in non-precious ORR catalysts, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0271ecst, 271-280, 2014.01, [URL], Iron-free, nitrogen-doped graphene foam is presented as a model electrocatalyst system for studying the role of nitrogen in the oxygen reduction reaction in non-precious Fe/N/C-based electrocatalysts. Due to the large surface area and high porosity, these electrocatalysts display high activity in rotating ring-disk electrode voltammetry measurements. The electron transfer number is as high as 3.6, despite the metal-free nature of this electrocatalyst. The sample with the highest activity has a significantly larger proportion of tertiary/graphite-like nitrogen, and therefore this is proposed as a 4-electron oxygen reduction active site in acid environment..
234. Jianfeng Liu, Daio Takeshi, Daniel Orejon, A. Kazunari Sasaki, Stephen Matthew Lyth, Defective nitrogen-doped graphene foam
A metal-free, non-precious electrocatalyst for the oxygen reduction reaction in acid, Journal of the Electrochemical Society, 10.1149/2.095404jes, 161, 4, F544-F550, 2014.01, [URL], Platinum-free oxygen reduction reaction (ORR) catalysts could help reduce the cost of future generations of polymer electrolyte membrane fuel cells (PEFCs). One class of non-precious catalyst for PEFCs are nanostructured Fe/C/N-based materials. In these, the nature of the active site is still hotly contested. Resolving this issue could lead to the development of better catalysts. One approach to achieve this is to study nitrogen-doped carbons, without any Fe content. Such materials have been studied, but largely in alkaline media where high activity is routinely obtained. Studies of metal-free catalysts in acid are rare, and Fe-contamination is often an issue. To truly shed light on the ORR mechanism of Fe/C/N-based catalysts, measurements on metal-free catalysts in acid media are required to simulate proton-based PEFC systems. Here we present synthesis of a metal-free defective nitrogen-doped graphene powder with remarkable surface area. We apply this as an ORR catalyst in acid medium and comment on the reaction mechanism..
235. Yasuto Minamida, Zhiyun Noda, Akari Hayashi, Kazunari Sasaki, Development of MEAs with Pt/mesoporous carbon as a cathode catalyst, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0137ecst, 137-144, 2014.01, [URL], With the aim of developing durable electrocatalysts for polymer electrolyte fuel cells, we have been working on Mesoporous Carbon (MC), composed by a nano-channel structure with the diameter of ca.10 nm. Based on the increased stability of metal particles on the curved surface comparing to the flat surface, Pt particles are encapsulated into the pores of MC and used as an electrocatalyst (Pt/MC). In this study, membrane-electrodeassemblies were developed with Pt/MC as a cathode catalyst. Their durability on the current-voltage response was evaluated using the potential cycle test at the potential range where the dissolution and re-precipitation of Pt particles occurs. As a result, increased durability has been demonstrated most likely because of reducing Pt mobility on the carbon support. Successful Nafion® introduction into nano-cahnnels of MC comes to a key factor to further increase both performance and durability..
236. Y. Nagamatsu, K. Kanda, Z. Noda, A. Hayashi, K. Sasaki, Electrochemical performance of MEAs with Pt/SnO2 mixed with conductive fillers, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0207ecst, 207-213, 2014.01, [URL], SnO2 can act an alternative PEFC electrocatalyst support to the conventional carbon black, for preventing catalyst support corrosion. In this study, current-voltage characteristics of MEAs with SnO2 support are improved by controlling the content of electron-conductive fillers and proton-conductive Nafion ionomer..
237. T. Bayer, S. R. Bishop, M. Nishihara, K. Sasaki, S. M. Lyth, Graphene oxide membrane fuel cells
Utilizing of a new class of ionic conductor, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0441ecst, 441-448, 2014.01, [URL], The characterization and application of graphene oxide membranes as fuel cell electrolytes is explored and presented. Morphology, chemical composition, mechanical and electrochemical properties of vacuum-filtration prepared graphene oxide membranes and their performance as fuel cell electrolytes are discussed. Our graphene oxide membrane fuel cell (GOMFC) showed a maximum power density of ∼ 6 mW/cm2 at 30 °C. Power density exhibited a decrease with increasing temperature and operation time, possibly due to partial loss of oxygen through reduction, and a resulting decrease in water-mediated proton transport..
238. Stephen Matthew Lyth, Huaiyu Shao, Jianfeng Liu, Kazunari Sasaki, Etsuo Akiba, Hydrogen adsorption on graphene foam synthesized by combustion of sodium ethoxide, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.10.044, 39, 1, 376-380, 2014.01, [URL], Hydrogen storage is a crucial technology for the realization of a carbon-neutral society. However, few materials have been able to approach useful hydrogen storage capacity at reasonable temperatures and pressures. Graphene has an extremely high surface-area-to-weight ratio, is strong, cheap, chemically inert, and environmentally benign. As such it may be an ideal substrate for hydrogen storage. Here we present synthesis of graphene foam by combustion of sodium ethoxide. This technique is low-cost, scalable, and results in a three-dimensional graphene network with a surface area of more than 1200 m 2/g. It is applied as a hydrogen storage material at liquid nitrogen temperature, with a capacity of 2.1 wt%..
239. Yasuo Kakihara, Yusuke Shiratori, Mio Sakamoto, Masaru Takada, Tomomi Uchida, Hao Le, Kazunari Sasaki, Hydrotalcite-dispersed paper-structured catalyst for dry reforming of methane, 20th World Hydrogen Energy Conference, WHEC 2014
20th World Hydrogen Energy Conference, WHEC 2014
, 1411-1415, 2014.01, High temperature solid oxide fuel cells (SOFCs) can accept the direct feed of hydrocarbon fuels which are reformed in the porous anode materials producing H2-rich syngas, subsequently used to generate electricity and heat through electrochemical oxidation. This type of SOFC is called direct internal reforming SOFC (DIR-SOFC). Now we try to overcome problems associated with the DIR-SOFC, such as carbon deposition caused by internal reforming, by applying a flexible structured-catalyst called paper-structured catalyst (PSC). Here, recent progresses are summarized focusing on the catalytic activity of hydrotalcite-containing PSCs for the dry reforming of methane..
240. Eunjoo Park, Shunsuke Taniguchi, Takeshi Daio, Jyh Tyng Chou, Kazunari Sasaki, Influence of cathode polarization on the chromium deposition near the cathode/electrolyte interface of SOFC, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.11.030, 39, 3, 1463-1475, 2014.01, [URL], Chromium poisoning phenomena were compared among three SOFC cathodes using (La0.8Sr0.2)0.98MnO3 (LSM), La 0.6Sr0.4Fe0.8Co0.2O3 (LSCF) and LaNi0.6Fe0.4O3 (LNF) at 700 C by changing cathode polarization (0-400 mV). Chromium vapor deposited near the electrolyte for LSM and LNF, and the amount of the deposition increased with increasing cathode polarization. In the case of LSCF, chromium deposited near the cathode surface under smaller cathode polarization (≤200 mV). Under larger cathode polarization (≥300 mV), however, chromium deposition near the cathode/electrolyte interface similarly increased for the three cathodes. Cathode polarization facilitated the chromium deposition and there seemed to be no correlation with the current density. Microscopic distribution of the deposited chromium, which was located on the surface of LSM, LSCF, LNF grains, and also on the surface of zirconia and ceria, seemed to correspond to the distribution of oxygen vacancy by cathode polarization at the electrode reaction sites. Chromium deposition on the zirconia surface seemed to be assisted by metal oxides segregated from the cathode material, which can conduct electron required for generating oxygen vacancy continuously. Oxygen deficiency on the surface of the deposited chromium was confirmed and interdiffusion of chromium and zirconium caused by cathode polarization was also suggested..
241. Masahiko Kitamura, Yasuto Minamida, Xiaojing Zhao, Zhiyun Noda, Akari Hayashi, Kazunari Sasaki, Investigation of performance and durability of MEAs at higher temperature, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0755ecst, 755-762, 2014.01, [URL], For the application of polymer electrolyte fuel cell (PEFC) as a next generation fuel cell vehicle, an increase in the operation temperature up to 120 °C is desired in order to improve the power generation efficiency. The objective of our research is to extract problems on catalytic degradation above 100 °C with the aim of developing durable electrocatalysts for future high temperature PEFC. In this study, we have prepared standard membrane-electrode-assemblies made with Nafion® membrane and evaluated their durability against carbon oxidation in the cathode layer under increased temperature like 105 °C. As a result, comparing to the standard operation condition (80 °C and RH100%), the degradation rate of their electrochemical performance was much more increased at higher temperature. Furthermore, a collapsed carbon structure in the cathode layer was clearly observed under the high temperature operation..
242. D. Horiguchi, T. Tsukatsune, Z. Noda, A. Hayashi, K. Sasaki, Pt/SnO2 electrocatalysts on conductive fillers, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14
, 10.1149/06403.0215ecst, 215-220, 2014.01, [URL], For polymer electrolyte fuel cells (PEFCs), corrosion of the carbon support of electrocatalysts under cathode conditions is one of the important technical issues to solve, for which SnO2 is a promising alternative support material. In this study, Pt/SnO2 electrocatalysts with integrated conductive fillers have been developed, where the fillers act as the backbone and the built-in electron-conductive pathway. Electrochemical activity and durability of such electrocatalysts against voltage cycling between 1.0 and 1.5 VRHE are investigated. This durable electrocatalyst exhibits higher the oxygen reduction reaction (ORR) activity than Pt/SnO2, and comparable ORR activity to that of the standard Pt/C electrocatalysts..
243. Jianfeng Liu, Daio Takeshi, Kazunari Sasaki, Stephen Matthew Lyth, Defective graphene foam
A platinum catalyst support for PEMFCs, Journal of the Electrochemical Society, 10.1149/2.0231409jes, 161, 9, F838-F844, 2014, [URL], Gram-scale synthesis of defective graphene foam from low-cost precursors is reported as a catalyst support material for platinum in fuel cell cathodes. The material was produced by combustion of sodium ethoxide, followed by washing and heat-treatment in various gases. The BET surface area is higher than 1500 m2/g. The defects in the material result in excellent distribution of platinum nanoparticles on the surface. The electrochemical performance is compared with platinum-decorated carbon black and commercially obtainable graphene using cyclic voltammetry, linear sweep voltammetry, andmembrane electrode assemblies. Pt-decorated grapheme foam has larger electrochemical surface area (101 m2/g) and higher mass activity (176 A/gPt). However, durability and fuel cell power density still require improvements. This graphene foam is a potentially useful catalyst support, especially for use in polymer electrolyte membrane fuel cells..
244. K. Kanda, Z. Noda, Y. Nagamatsu, T. Higashi, S. Taniguchi, S. M. Lyth, A. Hayashi, K. Sasaki, Negligible start-stop-cycle degradation in a PEFC utilizing platinum-decorated tin oxide electrocatalyst layers with carbon fiber filler, ECS Electrochemistry Letters, 10.1149/2.005404eel, 3, 4, F15-F18, 2014, [URL], Niobium-doped SnO2 is selected as an alternative carbon-free support material to negate carbon corrosion in polymer electrolyte fuel cells (PEFCs) electrocatalysts. The durability is measured using a membrane electrode assembly (MEA) over 60,000 start-stop cycles at high potential, equating to the lifetime of fuel cell vehicles. Using the Nb-doped SnO2 support results in retention of 99% of the initial cell voltage. The current-voltage characteristics are improved by adding carbon nanofibers as fillers in the Nb-doped SnO2, indicating that electronic conduction in the electrocatalyst layer is critical in the application ofmetal oxide-supported electrocatalysts..
245. T. Tsukatsune, Y. Takabatake, Z. Noda, T. Daio, A. Zaitsu, S. M. Lyth, A. Hayashi, K. Sasaki, Platinum-decorated tin oxide and niobium-doped tin oxide pefc electrocatalysts
Oxygen reduction reaction activity, Journal of the Electrochemical Society, 10.1149/2.0431412jes, 161, 12, F1208-F1213, 2014, [URL], Using tin oxide (SnO2) and niobium-doped tin oxide (Nb-SnO2) as alternative electrocatalyst support materials can effectively solve the issue of carbon corrosion in polymer electrolyte fuel cell (PEFC) cathodes. Here, we systematically explore the effect of support surface area, Pt loading, and Pt nanoparticle size on the electrochemistry of these carbon-free electrocatalysts. Reducing the Pt loading leads to an increase in electrochemical surface area, but the specific activity decreases as previously observed in conventional carbon based electrocatalysts. Removing residual chlorine impurities by replacing the H2PtCl6 nanoparticle precursor with Pt(acac)2 increases the specific activity. Niobium-doping of the SnO2 support also results in an increase in specific activity, due to the increased electronic conductivity. Consequently, the oxygen reduction reaction activity of optimized Pt-decorated Nb-SnO2 is approaching to that of Pt-decorated carbon black, the current state-of-the-art PEFC electrocatalyst..
246. Yoshinori KOBAYASHI, Kazuo TOMIDA, Hiroshi TSUKUDA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Durability of a Segmented-in-Series Tubular SOFC with a (Ce, Sm)O2 Cathode Interlayer: Influence of Operating Conditions, Journal of The Electrochemical Society, 161, 3, F214-F225, 2013.12.
247. Masamichi NISHIHARA, Liana CHRISTIANI, Aleksandar STAYKOV, Kazunari SASAKI, Experimental and Theoretical Study of Charge-Transfer Complex Hybrid Polyimide Membranes., Journal of Polymer Science, Part B: Polymer Physics, 52, 293-298, 2013.11.
248. Kazunari SASAKI, Tomoo YOSHIZUMI, Kengo HAGA, Hiroaki YOSHITOMI, Takami HOSOI, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Chemical Degradation of SOFCs: External Impurity Poisoning and Internal Diffusion-related Phenomena., ECS Transactions, 57, 1, 315-323, 2013.10.
249. Masahiro HANASAKI, Chie URYU, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Kazunari SASAKI, Durability of SOFC against Thermal and Redox Cycling., ECS Transactions, 57, 1, 691-697, 2013.10.
250. Yasuhiro TOYOFUKU, Takami HOSOI, Tsutomu KAWABATA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Durability of SOFCs using Inexpensive Ca-doped ZrO2 Electrolytes., ECS Transactions, 57, 1, 807-813, 2013.10.
251. Liang ZHAO, Kazunari SASAKI, Sean R. BISHOP, Fabrication and Characterization of Intermediate Temperature Solid Oxide Fuel Cells by Pulsed Laser Deposition., ECS Transactions, 57, 1, 843-848, 2013.10.
252. Junki SUGIMOTO, Tsutomu KAWABATA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Effect of Ceria Addition in SOFC Anodes on Sulfur Poisoning., ECS Transactions, 57, 1, 1395-1400, 2013.10.
253. Takami HOSOI, Takahiro YONEKURA, Kazunari SASAKI, Exchange Current Density of SOFC Anodes., ECS Transactions, 57, 1, 1585-1592, 2013.10.
254. Takashi NISHIMURA, Tsutomu KAWABATA, Yuya TACHIKAWA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, In-plane Distribution of Carbon Deposition on SOFCs., ECS Transactions, 57, 1, 1593-1598, 2013.10.
255. Liang ZHAO, Junji HYODO, Tatsumi Ishihara, Kazunari SASAKI, Sean R. BISHOP, XRD and Raman Spectroscopy Study of Mn Solubility in Cerium Oxide., ECS Transactions, 57, 1, 1607-1612, 2013.10.
256. Nicola H. PERRY, Daniele PERGOLESI, Kazunari SASAKI, Sean R. BISHOP, Harry L. TULLER, Influence of Donor Doping on Cathode Performance: (La, Sr)(Ti, Fe)O3-δ Case Study., ECS Transactions, 57, 1, 1719-1723, 2013.10.
257. Eunjoo PARK, Shunsuke TANIGUCHI, Takeshi DAIO, Jyh-Tyng CHOU, Kazunari SASAKI, Microscopic Observation on Deposited Chromium near the Cathode Reaction Site of SOFCs and Influence of Cathode Polarization Change., ECS Transactions, 57, 1, 1859-1864, 2013.10.
258. Sean R. BISHOP, John DRUCE, John KILNER, Tatsumi Ishihara, Kazunari SASAKI, Compensation for Oxygen Exchange Rate Limiting Impurities on a Pr0.1Ce0.9O2-δ SOFC Electrode Material., ECS Transactions, 57, 1, 2003-2007, 2013.10.
259. Hung Cuong PHAM, Eunjoo PARK, Shunsuke TANIGUCHI, Kazunari SASAKI, Development of a Porous Metal Substrate for Metal Supported SOFCs using a Fe-Cr-Al Stainless Steel., ECS Transactions, 57, 1, 2289-2293, 2013.10.
260. Yuya TACHIKAWA, Takami HOSOI, Takashi NISHIMURA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Computational Study of Performance Drop Phenomena Based on Sulfur Adsorption and Desorption Model in Planar-Type SOFCs., ECS Transactions, 57, 1, 2841-2848, 2013.10.
261. Yusuke SHIRATORI, Mio SAKAMOTO, Yutaro TAKAHASHI, Yuto WAKITA, Masaru TAKADA, Teppei OGURA, Hironori NAKAJIMA, Kazunari SASAKI, Development of Direct Internal Reforming SOFC Integrated with Paper-Structured Catalyst Fuelled by Biofuels., ECS Transactions, 57, 1, 2997-3004, 2013.10.
262. Quang Tuyen TRAN, Yusuke SHIRATORI, Yasuo KAKIHARA, Takuya KITAOKA, Kazunari SASAKI, Study on Fuel Composition for the Performance Enhancement of Solid Oxide Fuel Cell Operated with Biodiesel Fuel., ECS Transactions, 57, 1, 3005-3011, 2013.10.
263. Yoshio MATSUZAKI, Kazuo NAKAMURA, Takaaki SOMEKAWA, Kenjiro FUJITA, Teruhisa HORITA, Katsuhiko YAMAJI, Haruo KISHIMOTO, Masahiro YOSHIKAWA, Tohru YAMAMOTO, Yoshihiro MUGIKURA, Harumi YOKOKAWA, Naoki SHIKAZONO, Koichi EGUCHI, Toshiaki MATSUI, Satoshi WATANABE, Kazuhisa SATO, Toshiyuki HASHIDA, Tatsuya KAWADA, Kazunari SASAKI, Shunsuke TANIGUCHI, Multimodal Assessment of Durability and Reliability of Flattened Tubular SIS Stacks., ECS Transactions, 57, 1, 325-333, 2013.10.
264. Kohei ITO, Yang Ming HAO, Hironori NAKAJIMA, Hiroshi YOSHIZUMI, Kazunari SASAKI, Electrochemical characterization of hydrogen pump with internal humidifier and dead-end anode channel., ECS Transactions, 58, 1, 681-691, 2013.10.
265. Yasuto MINAMIDA, Xiaojing ZHAO, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Characterization of MEAs Fabricated by a Carbon Support with the Nano-Channel Structure., ECS Transactions, 58, 1, 1105-1111 , 2013.10.
266. Takuya TSUKATSUNE, Yuma TAKABATAKE, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Electrochemical Properties and Durability of Electrocatalysts Supported on SnO2., ECS Transactions, 58, 1, 1251-1257, 2013.10.
267. Takahiro HIGASHI, Zhiyun NODA, Akari HAYASHI, Kazunari SASAKI, Pulse Laser Deposition and Sputtering of Carbon-free Pt/SnO2 Electrocatalysts for PEFC., ECS Transactions, 58, 1, 1293-1299, 2013.10.
268. Jianfeng LIU, Kazunari SASAKI, Stephen Matthew LYTH, Electrochemical Oxygen Reduction on Metal-Free Nitrogen-Doped Graphene Foam in Acidic Media., ECS Transactions, 58, 1, 1529-1540, 2013.10.
269. Jianfeng LIU, Kazunari SASAKI, Stephen Matthew LYTH, Pt-decorated Graphene-like Foam for Electrochemical Oxygen Reduction with High Mass Activity., ECS Transactions, 58, 1, 1751-1762, 2013.10.
270. Yusuke Shiratori, Tran Quang-Tuyen, Yuuka Umemura, Takuya Kitaoka, Kazunari Sasaki, Paper-structured catalyst for the steam reforming of biodiesel fuel, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.06.080, 38, 26, 11278-11287, 2013.08, [URL], Architectonics of the paper-structured catalyst for the application to the biofuel reformer or direct internal reforming SOFC (DIRSOFC) was studied. Inorganic fiber network, "paper", composed of yttria-stabilized zirconia (YSZ) fiber (Zf), alumina fiber (Af) and inorganic binder (Al 2O3 sol (As) or ZrO2 sol (Zs) or CeO 2 sol (Cs)) was prepared by a simple paper-making process. Then, the catalytic activities of the Ni and Ni-MgO loaded papers called "paper-structured catalysts (PSCs)" for the steam reforming of biodiesel fuels (BDFs) were evaluated. Ni-MgO loaded PSC using Cs as an inorganic binder, Ni-MgO/ZfAfCs, exhibited excellent performance over Ru/γAl2O3 catalyst beads. Formation of light hydrocarbons, especially C2H4, was eliminated and water-gas shift reaction was more promoted compared to the catalyst beads..
271. Yusuke Shiratori, Tran Quang-Tuyen, Kazunari Sasaki, Performance enhancement of biodiesel fueled SOFC using paper-structured catalyst, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.05.128, 38, 23, 9856-9866, 2013.08, [URL], In this study, performance of solid oxide fuel cell (SOFC) connected with paper-structured catalyst (PSC) was evaluated in the direct feed of wet oleic fatty acid methyl ester (oleic-FAME, C19H36O2), which is a mono-unsaturated component of practical biodiesel fuels (BDFs), in the steam to carbon ratio (S/C) range between 2.0 and 3.5, and high current density of 1 A cm-2 (at 0.7 V) was recorded at 800 C. Long term stability of oleic-FAME fueled SOFC was achieved by the incorporation of PSC into SOFC even under severe operating condition prone to coking (direct feed of unsaturated hydrocarbon with carbon number 19 and low S/C ratio of 2.0). After 100 h test, coking was not observed in both SOFC anode and PSC..
272. Yusuke Shiratori, Teppei Ogura, Hironori Nakajima, Mio Sakamoto, Yutaro Takahashi, Yuto Wakita, Takuya Kitaoka, Kazunari Sasaki, Study on paper-structured catalyst for direct internal reforming SOFC fueled by the mixture of CH4 and CO2, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.06.046, 38, 25, 10542-10551, 2013.08, [URL], Inorganic fiber network including YSZ fiber which acts as catalyst support was created by the simple paper-making process, and novel Ni-loaded paper-structured catalysts(PSCs) with excellent catalytic activity for the dry reforming of methane were designed and developed. The PSCs exhibited high fuel conversion comparable to the conventional powdered catalysts with less than one-tenth catalyst weights. The significant advantages of the PSCs are their high mechanical flexibility and material workability. So far, a functionally-graded catalytic reaction field which leads to uniform temperature distribution during biogas reforming resulting in stable operation of planar SOFC was successfully developed by the PSC array based on the kinetic simulation model built in this research..
273. Yusuke SHIRATORI, Quang-Tuyen TRAN, Yuuka UMEMURA, Takuya KITAOKA, Kazunari SASAKI, Paper-structured Catalyst for the Steam Reforming of Biodiesel Fuel., Intl. J. of Hydrogen Energy, 38, 26, 11278-11287, 2013.07.
274. Liana CHRISTIANI, Masamichi NISHIHARA, Aleksandar STAYKOV, Kazunari SASAKI, Modification of Sulfonic Polyimides by Charge-transfer Complex Formation and Evaluation of its Proton Conductivity. , Proceedings of 4th European PEFC and H2 Forum 2013, A06, 9/53-16/53, 2013.07.
275. Kazunari SASAKI, Kohei KANDA, Yuma TAKABATAKE, Takuya TSUKATSUNE, Takahiro HIGASHI, Fumiaki TAKASAKI, Zhyun NODA, Akari HAYASHI, Alternative Electrocatalyst Support for PEFCs: SnO2-supported Carbon-free Electrocatalysts., Proceedings of 4th European PEFC and H2 Forum 2013, B07, 5/109-10/109, 2013.07.
276. Stephen Matthew LYTH, Jianfeng LIU, Kazunari SASAKI, Graphene Nano-foam as a Catalyst Support., Proceedings of 4th European PEFC and H2 Forum 2013, B07, 32/109-40/109, 2013.07.
277. Yusuke SHIRATORI, Teppei OGURA, Hironori NAKAJIMA, Mio SAKAMOTO, Yuraro TAKAHASHI, Yuto WAKITA, Takuya KITAOKA, Kazunari SASAKI, Study on Paper-structured Catalyst for Direct Internal Reforming SOFC Fueled by the Mixture of CH4 and CO2., Intl. J. of Hydrogen Energy, 38, 25, 10542-10551, 2013.07.
278. Yusuke SHIRATORI, Quang-Tuyen TRAN, Kazunari SASAKI, Performance Enhancement of Biodiesel Fueled SOFC using Paper-structured Catalyst., Intl. J. of Hydrogen Energy, 38, 23, 9856-9866, 2013.06.
279. Yuya Tachikawa, Zhiyun Noda, Akari Hayashi, Yusuke Shiratori, Kazunari Sasaki, Numerical analysis for evaluating the effect of hydrophilic anode support for water management in polymer electrolyte fuel cells, Theoretical and Applied Mechanics Japan, 61, 161-172, 2013.06, Much attempt was made to improve PEFC perfonnance to optimize its operating condition and its structure by experimental and numerical trials. One of the most critical issues about PEFC improvement is the durability enhancement at its membrane electrode assembly (MEA) to keep its robust control. The objective of this study is to keep the optimal water distribution at MEA with applying the hydrophilic anode support. In this study, the influence of modification to use two hydrophilic support materials is calculated by the case of weak hydrophilized carbon support and strong hydrophilic SnC>2 support. The distribution of liquid water shows that hydrophilic anode support has the effect to hold the liquid water in anode catalyst layer under the low humidification, and water saturation ratio in cathode catalyst layer is also controlled by the use of hydrophilic materials. Hydrophilic anode support works as a water transport pathway to anode across polymer electrolyte membrane. Its effect also prevents from drying-up of the anode and flooding of the cathode..
280. Mohamed R. Berber, Tsuyohiko Fujigaya, Kazunari Sasaki, Naotoshi Nakashima, Remarkably durable high temperature polymer electrolyte fuel cell based on poly(vinylphosphonic acid)-doped polybenzimidazole, Scientific reports, 10.1038/srep01764, 3, 2013.06, [URL], Low durability of polymer electrolyte fuel cell (PEFC) is a major drawback that should be solved. Recent studies have revealed that leaching of liquid phosphoric acid (PA) from both polymer electrolyte membrane and catalyst layers causes inhomogeneous PA distribution that results in deterioration of PEFC performance during long-term operation. Here we describe the finding that a novel PEFC free from acid leaching shows remarkable high durability (single cell test: >400,000 cycling) together with a high power density at 120 C under a non-humidified condition. This is achieved by using a membrane electrode assembly (MEA) with Pt on poly(vinylphosphonic acid)-doped polybenzimidazole wrapped on carbon nanotube and poly(vinylphosphonic acid)-doped polybenzimidazole for the electrocatalst and electrolyte membrane, respectively. Such a high performance PEFC opens the door for the next-generation PEFC for "real world" use..
281. Xiaojing ZHAO, Akari HAYASHI, Zhiyun NODA, Kazunari SASAKI, Development of Durable Electrocatalysts for PEFC through Graphitization of Carbon Support Surface., ECS Transactions, 53, 12, 23-29, 2013.05.
282. Yuya TACHIKAWA, Zhiyun NODA, Akari HAYASHI, Yusuke SHIRATORI, Kazunari SASAKI, Numerical Analysis for Evaluating the Effect of Hydrophilic Anode Support for Water Management in Polymer Electrolyte Fuel Cells., Theoretical and Applied Mechanics Japan, 61, 161-172, 2013.05.
283. Tran Quang-Tuyen, Yusuke Shiratori, Kazunari Sasaki, Feasibility of palm-biodiesel fuel for a direct internal reforming solid oxide fuel cell, International Journal of Energy Research, 10.1002/er.2883, 37, 6, 609-616, 2013.05, [URL], The feasibility of a direct internal reforming (DIR) solid oxide fuel cell (SOFC) running on wet palm-biodiesel fuel (BDF) was demonstrated. Simultaneous production of H2-rich syngas and electricity from BDF could be achieved. A power density of 0.32Wcm-2 was obtained at 0.4 A cm-2 and 800°C under steam to carbon ratio of 3.5. Subsequent durability testing revealed that a DIR-SOFC running on wet palm-BDF exhibited a stable voltage of around 0.8V at 0.2 A cm-2 for more than 1month with a degradation rate of approximately 15 % / 1000h. The main cause of the degradation was an increase in the ohmic resistance..
284. Eunjoo PARK, Shunsuke TANIGUCHI, Jyh-Tyng CHOU, Yuya TACHIKAWA, Yusuke Shiratori, Kazunari SASAKI, Influence of Cathode Polarization on the Chromium Poisoning of SOFC Cathodes Consisting of LSM, LSCF and LNF., ECS Transactions, 10.1149/05030.0021ecst, 50, 30, 21-25, 2013.04.
285. Liang ZHAO, BISHOP SEAN, Junji Hyodo, Tatsumi Ishihara, Kazunari SASAKI, XRD and Raman spectroscopy study of Fe solubility in cerium oxide., ECS Transactions, 10.1149/05040.0053ecst, 50, 40, 53-58, 2013.04.
286. Xiaojing ZHAO, Akari Hayashi, Zhiyun NODA, Ken’ichi KIMIJIMA, Ichizo YAGI, Kazunari SASAKI, Evaluation of Change in Nanostructure through the Heat Treatment of Carbon Materials and their Durability for the Start/Stop Operation of Polymer Electrolyte Fuel Cells., Electrochimica Acta, 10.1016/j.electacta.2013.02.062, 97, 33-41, 2013.03.
287. Xiaojing Zhao, Akari Hayashi, Zhiyun Noda, Kazunari Sasaki, Development of durable electrocatalysts for PEFC through graphitization of carbon support surface, Symposium on Advances in Low Temperature Electrolyzer and Fuel Cell Technology: In Honor of Anthony B. (Tony) LaConti - 223rd Meeting of the Electrochemical Society
Advances in Low Temperature Electrolyzer and Fuel Cell Technology
In Honor of Anthony B. (Tony) LaConti
, 10.1149/05312.0023ecst, 23-29, 2013.01, [URL], With the aim of developing durable electrocatalysts for PEFC, their durability with different carbon supports was evaluated electrochemically. During our study, Pt deposited Ketjen Black carbon was found to lose most of electrochemical active surface area after the potential cycle tests, and then a possible mechanism for that was investigated. We believe two different mechanisms probably occur at the same time. Many of Pt particles are dissolved into the electrolyte solution either as Pt ion or Pt nanoparticles. Some of Pt particles are also embedded into the hole formed on the carbon surface owing to carbon corrosion. However, the effect of these two factors was rather small for Vulcan carbon. Moreover, on the graphitized surface, such problems were mostly overcome. Consequently, graphitization of the carbon surface is a simple but useful technique to improve the durability of electrocatalysts..
288. Xiaojing Zhao, Akari Hayashi, Zhiyun Noda, Kazunari Sasaki, Evaluation of MEAs prepared by Pt/C electrocatalysts with improved durability through the heat treatment, ECS Transactions, 10.1149/05824.0007ecst, 58, 24, 7-13, 2013.01, [URL], With the aim of developing durable electrocatalysts for polymer electrolyte fuel cells, their durability with different carbon supports have been evaluated electrochemically in our study. During our previous investigation, we have found that graphitization of carbon surface through the heat treatment at appropriate temperature is a simple but useful technique to improve the durability of electrocatalysts. Especially, a electrocatalyst made by heat treatment of Vulcan carbon at 1600 °C, Pt/GVC1600, has shown much more improved durability than one made without heat treatment, Pt/VC, in the half-cell evaluation. In this study, MEA with Pt/GVC1600 for the cathode was developed and evaluated. Initial performance of MEA was found to be almost the same between these two catalysts, but regarding to durability, Pt/GVC1600 showed much more improved durability than Pt/VC. Heat treatment of carbon supports at optimum temperature lead to increasing in durability not only in the half-cell but also in the full-cell..
289. Yasuto Minamida, Xiaojing Zhao, Zhiyun Noda, Akari Hayashi, Kazunari Sasaki, Characterization of MEAs fabricated by a carbon support with the nano-channel structure, ECS Transactions, 10.1149/05801.1105ecst, 58, 1, 1105-1111, 2013, [URL], With the aim of developing durable electrocatalysts for polymer electrolyte fuel cells, we have been working on Mesoporous Carbon (MC) with the nano-channel structure, whose diameter is ca. 10 nm. By encapsulating Pt catalysts into the pores of MC, improvement of oxygen reduction reaction activity and durability, comparing to Pt deposited on conventional carbon, has been observed in the half-cell evaluation. Improvement on its durability is mainly due to the reduced mobility of Pt particles within pores of MC. In this study, MEAs were newly developed using Pt deposited MC as a cathode catalyst. By controlling the amount of Nafion® and adding a heat treatment step after ball-milling of MC, MEA with IV performance, comparable to Pt deposited on conventional carbon, was successfully developed..
290. K. Sasaki, T. Yoshizumi, K. Haga, H. Yoshitomi, T. Hosoi, Y. Shiratori, S. Taniguchi, Chemical degradation of SOFCs
External impurity poisoning and internal diffusion-related phenomena, ECS Transactions, 10.1149/05701.0315ecst, 57, 1, 315-323, 2013, [URL], Durability of SOFCs is one of the most important requirements for commercialization. In this paper, we analyze chemical degradation phenomena caused by both extrinsic and intrinsic origins besides by thermal/redox cycling. As external degradation, impurity (sulfur, phosphorus etc.) poisoning has been systematically analyzed and classified based on both thermochemical and kinetic consideration. We present typical intrinsic chemical degradation phenomena observed, mainly diffusion-related processes (interdiffusion, grain boundary diffusion, dopant dissolution, phase transformation etc.) around interfaces between the electrolyte and the electrode, which has been revealed through high-resolution STEM-EDX analysis of cells after long-term operation. Degradation mechanisms have been classified..
291. S. R. Bishop, J. Druce, J. Kilner, T. Ishihara, K. Sasaki, Compensation for oxygen exchange rate limiting impurities on a Pr 0.1Ce0.9O2-™SOFC electrode material, ECS Transactions, 10.1149/05701.2003ecst, 57, 1, 2003-2007, 2013, [URL], Impurities on the surface of SOFC electrodes can dramatically reduce their interfacial transport. In this work, we use a novel in situ optical absorption relaxation technique to derive the oxygen exchange rate in the absence of electrodes, thereby studying the "innate" material. Si is found to be an impurity in high concentration, with its presence associated with an orders of magnitude decrease in oxygen exchange rate. Addition of La to the electrode surface is found to substantially improve oxygen exchange rate..
292. Y. Tachikawa, T. Hosoi, T. Nishimura, Y. Shiratori, S. Taniguchi, K. Sasaki, Computational study of performance drop phenomena based on sulfur adsorption and desorption model in planar-type SOFCs, ECS Transactions, 10.1149/05701.2841ecst, 57, 1, 2841-2848, 2013, [URL], For solid oxide fuel cell (SOFC) systems operating with practical fuels, it is important to simulate the distribution of sulfur poisoning and its dependence on the operating conditions in planar-type SOFCs. In this paper, by taking into account the sulfur poisoning effect and its distribution in planar-type SOFC simulation, numerical analysis is performed using anode exchange current density data and Temkin-like sulfur adsorption isotherm on Ni surface. From this numerical analysis, it is found that the distribution of current density after sulfur poisoning is changed, depending on operating temperature and fuel utilization..
293. H. C. Pham, E. Park, S. Taniguchi, K. Sasaki, Development of a porous metal substrate for metal supported SOFCs using a Fe-Cr-Al stainless steel, ECS Transactions, 10.1149/05701.2289ecst, 57, 1, 2289-2293, 2013, [URL], Metal supported cells with porous metallic substrates made of stainless steels are expected to drastically improve remaining issues of durability and cost for solid oxide fuel cells (SOFCs). In this study, we succeeded in fabricating a porous alloy substrate for SOFC using a Fe-Cr-Al type stainless steel, which showed excellent heat resistance. We investigated the application of the alloy substrate for the cathode side and good heat resistance and relatively low contact resistance between the alloy substrate and La 0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was obtained at 700°C in air..
294. Y. Shiratori, M. Sakamoto, Y. Takahashi, Y. Wakita, M. Takada, T. Ogura, H. Nakajima, K. Sasaki, Development of direct internal reforming SOFC integrated with paper-structured catalyst fuelled by biofuels, ECS Transactions, 10.1149/05701.2997ecst, 57, 1, 2997-3004, 2013, [URL], Flexible Ni-loaded paper-structured catalysts (PSCs) were prepared by the simple paper-making process. Stable performance of DIRSOFC fuelled by simulated biogas mixture (CH4/CO2 = 1) was demonstrated by the integration of electrolyte-supported cell with PSC array which leads to uniform in-plane reaction distribution. Anode-supported cell stacked with PSC exhibited maximum power density of 820 mW cm-2 and degradation rate of 1.4 %/1000 h at 750 °C in the direct feed of biogas mixture without humidification..
295. M. Hanasaki, C. Uryu, S. Taniguchi, Y. Shiratori, K. Sasaki, Durability of SOFC against thermal and redox cycling, ECS Transactions, 10.1149/05701.0691ecst, 57, 1, 691-697, 2013, [URL], Durability of cells and stacks against thermal cycling and redox cycling is essential for practical SOFCs, in which the system experiences various kinds of cycling conditions, including the shutoff of fuel supply. In this study, we have investigated the influence of thermal cycling conditions, such as hot-standby, cold-standby, and shut-down, on the cell performance degradation..
296. Y. Toyofuku, T. Hosoi, T. Kawabata, Y. Shiratori, S. Taniguchi, K. Sasaki, Durability of SOFCs using inexpensive Ca-doped ZrO2 electrolytes, ECS Transactions, 10.1149/05701.0807ecst, 57, 1, 807-813, 2013, [URL], For the further commercialization of SOFCs, the cost reduction for materials is one of the most important technological issues. Currently, Y or Sc is widely used as a dopant of zirconia-based electrolytes, but these rare-earth elements are relatively expensive. In this study, we have examined the possibility to use Ca as an alternative dopant since it is abundant in the earth and inexpensive. We have experimentally found that Ca diffusion is relatively fast, causing cell performance degradation. Even so, such fast diffusion could be depressed by decreasing the concentration gradient of Ca dopant, leading to an improvement in the durability..
297. J. Sugimoto, T. Kawabata, Y. Shiratori, S. Taniguchi, K. Sasaki, Effect of ceria addition in SOFC anodes on sulfur poisoning, ECS Transactions, 10.1149/05701.1395ecst, 57, 1, 1395-1400, 2013, [URL], In SOFCs, a wide range of fuel gases can be applied, but fuel impurity tolerance may be desired. By applying gadolinia-doped ceria (GDC) anode material, we analyzed power generation characteristics and internal reforming followed by high-resolution electron microscopy in order to moderate sulfur poisoning. Effect of ceria addition into the anodes layers on sulfur poisoning is systematically analyzed and discussed..
298. Kohei Ito, Yang Ming Hao, Hironori Nakajima, Hiroshi Yoshizumi, Kazunari Sasaki, Electrochemical characterization of hydrogen pump with internal humidifier and dead-end anode channel, ECS Transactions, 10.1149/05801.0681ecst, 58, 1, 681-691, 2013, [URL], Hydrogen gas is compressed with a new electrochemical pump, where internal humidifier is built in, and dead-end at anode is considered for a practical situation. Both the voltage and current efficiency of the hydrogen pump is evaluated experimentally. The pump is operated up to 2 MPaG under the temperature condition of 293 and 333 K. The voltage efficiency indicates nearly 50% at most and the maximum current efficiency is 96%. Overpotentials inherently involved in the pump are discussed with electrochemical impedance spectroscopy..
299. Jianfeng Liu, Kazunari Sasaki, Stephen Matthew Lyth, Electrochemical oxygen reduction on metal-free nitrogen-doped graphene foam in acidic media, ECS Transactions, 10.1149/05801.1529ecst, 58, 1, 1529-1540, 2013, [URL], Non-precious oxygen reduction reaction (ORR) catalysts could help reduce the cost of future generations of polymer electrolyte membrane fuel cells (PEFCs). One class of Pt-free catalysts for PEFCs are nanostructured Fe/C/N-based materials. In these, the nature of the active site is still hotly contested. Resolving this issue could lead to the development of better catalysts. One approach to achieve this is to study nitrogen-doped carbons which do not contain any Fe. Such materials have been studied, but largely in alkaline media where high activity is obtained. To truly understand the ORR mechanism of Fe/C/N-based catalysts, measurements in acid media are required to simulate the activity in proton-based PEFC systems. Here we present bulk synthesis of a metal-free nitrogen-doped graphene powder with remarkable surface area. We apply this as an ORR catalyst in acid media and comment on the reaction mechanism..
300. T. Tsukatsunea, Y. Takabatakea, Z. Nodab, A. Hayashi, K. Sasakia, Electrochemical properties and durability of electrocatalysts supported on SnO2, ECS Transactions, 10.1149/05801.1251ecst, 58, 1, 1251-1257, 2013, [URL], For polymer electrolyte fuel cells (PEFCs), carbon corrosion, leading to lower activities of catalysts under cathode conditions, is one of the important technological issues to be solved. We have been developing SnO2 and Nb-SnO2 as alternative support materials. In this study, the oxygen reduction reaction (ORR) activity and the durability of Pt/SnO2 and Pt/Sn0.98Nb0.02O2 against voltage cycling between 1.0 and 1.5 VRHE are quantitatively investigated. Longer ORR durability was verified, compared to the standard catalyst, Pt/Vulcan. Furthermore, we have found that the degradation mechanism of ORR is probably different between carbon black and SnO2-based supports. In the case of SnO2-based catalysts, degradation arose mainly from the loss of electrochemical surface area (ECSA), while other factors were also involved for Pt/Vulcan. Consequently, SnO2 is a promising candidate electrocatalyst support material to solve carbon corrosion problems of PEFCs..
301. T. Hosoi, T. Yonekura, K. Sasaki, Exchange current density of SOFC anodes, ECS Transactions, 10.1149/05701.1585ecst, 57, 1, 1585-1592, 2013, [URL], While Solid Oxide Fuel Cells (SOFCs) have attracted increasing attention, there are only a limited number of papers on exchange current density, representing electrode activity to describe and simulate SOFC performance. In this study, theoretical relationships on anode exchange current density have been derived as a function of various operational parameters by taking into account elementary reaction processes. Analytical relations under various boundary conditions are also derived with respect to gas partial pressures..
302. L. Zhao, K. Sasaki, S. R. Bishop, Fabrication and characterization of intermediate temperature solid oxide fuel cells by pulsed laser deposition, ECS Transactions, 10.1149/05701.0843ecst, 57, 1, 843-848, 2013, [URL], Decreasing the operating temperature in solid oxide fuel cells (SOFCs) will aid in increasing their portability and durability. However, the electrolyte and electrode resistances increase significantly at lower temperatures. Pulsed Laser deposition (PLD) is a promising method to prepare thin films, thus reducing the ohmic resistance of the electrolyte and electrode, with microstructural and morphological control depending on deposition conditions, keys to maximizing electrode electrochemical performance. In this research, SOFC cells consisting of anode/electrolyte/cathode thin film layers grown by PLD on electrically conductive porous supports were fabricated. The microstructure control of cathode and anode functional layers in different deposition conditions are discussed..
303. T. Nishimura, T. Kawabata, Y. Tachikawa, Y. Shiratori, S. Taniguchi, K. Sasaki, In-plane distribution of carbon deposition on SOFCs, ECS Transactions, 10.1149/05701.1593ecst, 57, 1, 1593-1598, 2013, [URL], SOFC can directly utilize not only hydrogen but also various fuels such as city gas, kerosene, and others by internal reforming reaction on anodes. However, impurities and un-reformed hydrocarbon in fuels can cause degradation associated with carbon deposition. In this study, in-plane distribution of carbon deposition was evaluated using planar cells with an electrode area of 4 cm by 4 cm. The 2-dimensional distribution of deposited carbon has been visualized, where the carbon deposition was accelerated in the coexistence of C3H8 and H2S as minor constituents in simulated prereformed CH4-based fuels..
304. N. H. Perry, D. Pergolesi, K. Sasaki, S. R. Bishop, H. L. Tuller, Influence of donor doping on cathode performance
(La,Sr)(Ti,Fe)O 3-δ case study, ECS Transactions, 10.1149/05701.1719ecst, 57, 1, 1719-1723, 2013, [URL], Donor doping of the p-type solid oxide fuel cell cathode, Sr(Ti,Fe)O 3-δ, with La was pursued to examine the role of minority charge carriers (electrons) on the oxygen exchange rate. Model dense thin film cathodes of (La,Sr)(Ti,Fe)O3-δ were fabricated by pulsed laser deposition. Optical transmission spectroscopy measurements demonstrated that the addition of the donor La resulted in a change in valence state of Fe from 4+ to 3+, suggesting a rise in Fermi level. The activation energy of the cathode's area specific resistance, studied by impedance spectroscopy, was found to be lower with La addition; however, the magnitude of the area specific resistance was not lowered..
305. Eunjoo Park, Shunsuke Taniguchi, Takeshi Daio, Jyh Tyng Chou, Kazunari Sasaki, Microscopic observation on deposited chromium near the cathode reaction site of SOFCs and influence of cathode polarization change, ECS Transactions, 10.1149/05701.1859ecst, 57, 1, 1859-1864, 2013, [URL], We already clarified that chromium deposition near the cathode/electrolyte interface was predominantly affected by the cathode polarization and the chromium deposition occurred not only on the cathode materials (LSM, LSCF etc.) but also on the electrolyte material, which seems to be involved in the electrode reaction sites. In this study, influence of cathode polarization change on the distribution of the deposited chromium was investigated by using LSM cathode. Microstructure at the cathode/electrolyte interface seems to change by cathode polarization and the microscopic distribution of the deposited chromium can be affected by the change in the microstructure..
306. Y. Matsuzaki, K. Nakamura, T. Somekawa, K. Fujita, T. Horita, K. Yamaji, H. Kishimoto, M. Yoshikawa, T. Yamamoto, Y. Mugikura, H. Yokokawa, N. Shikazono, K. Eguchi, T. Matsui, S. Watanabe, K. Sato, T. Hashida, T. Kawada, K. Sasaki, S. Taniguchi, Multimodal assessment of durability and reliability of flattened tubular SIS stacks, ECS Transactions, 10.1149/05701.0325ecst, 57, 1, 325-333, 2013, [URL], The durability and reliability of segmented-in-series (SIS) type cellsstack was investigated by multimodal assessment in which Tokyo Gas collaborated with research institutes under NEDO project, "Development of system and elemental technology on SOFCs". The SIS cells-stack, developed by Tokyo Gas in cooperation with Kyocera, has many advantages such as reduced temperature operation, highvoltage / low-current power generation, and lower in material cost of electrical insulating substrate compared to Ni based substrates for anode-supported cells. Another key advantage is that there is no need for alloy interconnects. This would make the cell-stack more durable than other types of cell-stacks having metallic interconnects. Durability of the stacks was investigated by the operations in electric furnaces at Tokyo Gas, Central Research Institute of Electric Power Industry (CRIEPI), and Kyushu University. After the operations post analyses were conducted by the research institutes, such as National Institute of Advanced Industrial Science and Technology (AIST), Tohoku University, Kyoto University, The University Tokyo, and Kyushu University. Through the multimodal assessment durability and reliability of the SIS stacks for long-term operation and thermal cycles have been shown to be high enough for 40,000 h life and more..
307. Jianfeng Liu, Kazunari Sasaki, Stephen Matthew Lyth, Pt-decorated graphene-like foam for electrochemical oxygen reduction with high mass activity, ECS Transactions, 10.1149/05801.1751ecst, 58, 1, 1751-1762, 2013, [URL], Gram-scale synthesis of graphene-like foam from low cost precursors is reported as a support material for platinum in fuel cell cathodes. The graphene-like foam was produced by combustion of sodium ethoxide, followed by washing and heat treatment in various gases. The BET surface area is higher than 1500 m2/g, although the material is highly defective. These defects result in an excellent distribution of platinum nanoparticles on the surface. The electrochemical performance of the resulting electrocatalysts are characterized using cyclic voltammetry and linear sweep voltammetry techniques, which reveal that this Pt-decorated graphene has large electrochemical surface area (101 m2/g) and high mass activity for the oxygen reduction reaction (176 A/gPt), making this graphene-like foam a potentially useful catalyst support for use in polymer electrolyte membrane fuel cells..
308. T. Higashi, Z. Noda, A. Hayashi, K. Sasakia, Pulse laser deposition and sputtering of carbon-free Pt/SnO2 electrocatalysts for PEFC, ECS Transactions, 10.1149/05801.1293ecst, 58, 1, 1293-1299, 2013, [URL], Polymer electrolyte fuel cells (PEFCs) are one of the promising future power sources. Even though technologies for PEFC are mostly developed, durability of their electrocatalysts is one of the most important issues for further development. In order to improve the durability against carbon corrosion problem, we have been working on carbon-free Pt electrocatalysts using SnO 2 and demonstrating improved durability. However, SnO 2-supported electrocatalysts often result in lower performance mainly due to relatively high contact resistance between SnO2 particles. In this study, an attempt has been made to develop an alternative way to fabricate the SnO2-based cathode using pulse laser deposition (PLD) and ion plasma sputtering in order to reduce the contact resistance. Consequently, the use of the doped-SnO2 thin layer has lowered the overpotential of cathode reactions, resulting in successful development of PEFC consisting of SnO2-supported cathode with both high power performance and durability..
309. Q. T. Tran, Y. Shiratori, Y. Kakihara, T. Kitaoka, K. Sasaki, Study on fuel composition for the performance enhancement of solid oxide fuel cell operated with biodiesel fuel, ECS Transactions, 10.1149/05701.3005ecst, 57, 1, 3005-3011, 2013, [URL], In principle, direct internal reforming of practical biodiesel fuels (BDFs) in a solid oxide fuel cell (SOFC) is viable. However, direct feed of practical BDFs to a SOFC caused severe carbon deposition accompanied by C 2H4 formation, which were more significant for higher degree of unsaturation of BDFs. Performance of SOFC running on BDF can be enhanced by increasing the content of a fatty acid methyl ester (FAME) with lower degree of unsaturation. To suppress formation of carbon and C 2H4, a flexible catalyst composed of inorganic fiber network was applied for the operation of SOFC running on FAMEs. In this study, rather high power density of 0.84 W cm-2 at 0.7 V was achieved in the feed of a mixture of oleic- and palmitic-FAMEs..
310. L. Zhao, J. Hyodo, T. Ishihara, K. Sasaki, S. R. Bishop, XRD and raman spectroscopy study of Mn solubility in cerium oxide, ECS Transactions, 10.1149/05701.1607ecst, 57, 1, 1607-1612, 2013, [URL], The solubility of Mn in CeO2 was investigated for 3-50 mol% Mn. Powders were synthesized by the Pechini method in air. Raman spectroscopy and lattice parameter analysis revealed that the solubility limit of Mn in CeO2 is less than 3 mol% for the present preparation conditions. The low solubility limit was rationalized in terms of the much smaller ionic radius of Mn versus Ce. As a consequence, an approach to increase the Mn radii size through annealing in reducing conditions (humidified H2 at 1100 °C) was attempted. In this case, the MnO phase was observed by XRD, thereby indicating difficulty in obtaining Mn doped CeO2 under reducing conditions, as well..
311. A. Hayashi, I. Yagi, K. Kimijima, K. Sasaki, Electrochemistry in nano-space of structurally controlled carbon materials, Electrochemistry at Nanoscale Dimensions 2 - 220th ECS Meeting
Electrochemistry at Nanoscale Dimensions 2
, 10.1149/1.3684482, 15-23, 2012.12, [URL], For the purpose of studying electrochemical reactions in nanospace of structurally controlled carbon, electrochemistry inside the hydrophobic 8 nm pores with platinum deposited mesoporous carbon (Pt/MC) was investigated, and reaction selectivity within carbon nano-space was demonstrated. Distinctive activities toward hydrogen evolution/oxidation and oxygen evolution reactions were observed, comparing to reactions in larger pores (>30 nm). Only small amount of water is expected to exist within such small nano-space even though a proton pass is effectively maintained. Consequently, selectivity in reactions, such as activation of proton-related reactions and suppression of water-related reactions, is achieved by Pt/MC electrocalatysts..
312. Stephen M. Lyth, Jianfeng Liu, Kazunari Sasaki, Electrochemical oxygen reduction on nitrogen-containing graphene, 2012 12th IEEE International Conference on Nanotechnology, NANO 2012
2012 12th IEEE International Conference on Nanotechnology, NANO 2012
, 10.1109/NANO.2012.6322162, 2012.11, [URL], Graphene is ideally suited to electrochemistry by virtue of its high surface area and impressive electronic properties. Nitrogen incorporation can be used to tailor the properties of graphene. Here we present a simple solvothermal technique to produce a nitrogen-containing foam-like macroporous graphene powder doped with up to 15 wt% nitrogen. This is applied as an effective non-precious, metal-free electrochemical catalyst for oxygen reduction in acid media..
313. Zhiyun NODA, Kyohei HIRATA, Akari Hayashi, Shunsuke TANIGUCHI,, Naoto NAKAZATO, Atsuko SEO, Isamu YASUDA, Seiji ARIURA, Hidetoshi SHINKAI, Kazunari SASAKI, PEFC-type Impurity Sensors for Hydrogen Fuels., Intl. J. of Hydrogen Energy, 10.1016/j.ijhydene.2012.08.062, 37, 21, 16256-16263, 2012.09.
314. Tomoo YOSHIZUMI, Shunsuke TANIGUCHI, Yusuke Shiratori, Kazunari SASAKI, Sulfur Poisoning of SOFCs: Voltage Oscillation and Ni Oxidation., J. Electrochem. Soc., 10.1149/2.032211jes, 159, 11, F693-F701, 2012.08.
315. Chuanjun LIU, Zhiyun Noda, Kazunari SASAKI, Kenshi Hayashi, Development of a Polyaniline Nanofiber-based Carbon Monoxide Sensor for Hydrogen Fuel Cell Application., Intl. J. o f Hydrogen Energy, 10.1016/j.ijhydene.2012.06.096, 37, 13529-13535, 2012.07.
316. Kazunari SASAKI, Kengo HAGA, Tomoo YOSHIZUMI, Hiroaki YOSHITOMI, Kota MIYOSHI, Shunsuke TANIGUCHI, Yusuke Shiratori, Chemical Degradation of SOFCs: External impurity poisoning and internal diffusion-related phenomena., Proceedings of10th European SOFC Forum 2012, A12_5-13, 2012.06.
317. Yuto WAKITA, Yutaro TAKAHASHI, Tuyen Quang TRAN, Yusuke Shiratori, Kazunari SASAKI, Technical Issues of Direct Internal Reforming SOFC(DIRSOFC) operated by Biofuels., Proceedings of10th European SOFC Forum 2012, B11_128-136, 2012.06.
318. Yutaro TAKAHASHI, Yusuke Shiratori, Sachiko FURUTA, Kazunari SASAKI, Thermo-mechanical Reliability and Catalytic activity of Ni–Zirconia Anode Supports in Internal Reforming SOFC Running on Biogas ., Solid State Ionics, 10.1016/j.ssi.2012.03.038, 225, 113-117, 2012.04.
319. Tuyen Quang TRAN, Yusuke Shiratori, Kazunari SASAKI, Feasibility of Palm-biodiesel Fuel for a Direct Internal Reforming Solid Oxide Fuel Cell., Intl. J. of Energy Research, 37, 609-616, 2012.02.
320. Akari Hayashi, Ichizo YAGI, Ken’ichi KIMIJIMA, Kazunari SASAKI, Electrochemistry in Nano-Space of Structurally Controlled Carbon Materials., ECS Transactions, 41, 19, 15-23, 2012.01.
321. Kazunari Sasaki, A future carbon-free fuel - Hydrogen, Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering, 10.2493/jjspe.78.27, 78, 1, 27-30, 2012.01, [URL].
322. Y. Shiratori, T. Q. Tran, Y. Takahashi, K. Sasaki, Application of biofuels to solid oxide fuel cell, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570264, 2641-2651, 2011.12, [URL], Performance of internal reforming SOFC was evaluated in the temperature range of 700-800°C for various biofuels. Three real biodiesel fuels (BDFs) and two pure fatty acid methyl esters (FAMEs) with different contents of unsaturated C-C bonds were fed directly to anode-supported SOFCs. The results demonstrated that in principle direct-feeding of BDFs into SOFC is viable, but the content of unsaturated FAMEs in BDF should be as low as possible. Direct feeding of BDFs caused carbon deposition which was more significant at lower operational temperatures and at higher contents of unsaturated FAMEs. On the other hand, biogas obtained by anaerobic fermentation of garbage, is suitable for SOFC operation because it contains natural reforming agent (CO 2). Stable operation of internal reforming SOFC running on biogas was achieved by the addition of adequate amount of air to biogas..
323. Harumi Yokokawa, Haruo Kishimoto, Katsuhiko Yamaji, Teruhisa Horita, Takao Watanabe, Tohru Yamamoto, Koichi Eguchi, Toshiaki Matsui, Kazunari Sasaki, Yusuke Shiratori, Tatsuya Kawada, Kazuhisa Sato, Toshiyuki Hashida, Atsushi Unemoto, Tatsuo Kabata, Kazuo Tomida, Cooperative investigations on degradation of cathode materials in segment-in-series cells by MHI, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570212, 2191-2200, 2011.12, [URL], Segment-in-series cell fabricated by Mitsubishi Heavy Industries have been investigated from various experimental approaches. Examined samples are type 1 cells which were operated for up to 10,000 h by CRIEPI. Analyses were made by AIST on materials transport with dynamic SIMS, by CRIEPI on microstructure observation with EPMA, by Kyoto University on microstructure change with FIB-SEM, by Kyushu University on chemical states with S-TEM, and by Tohoku University on mechanical properties in the microscopic zone with micro indentation technique. On the bases of accumulated knowledge on these samples, the materials deterioration model has been established with a focus on the movement of the Ca component in the cathode layers. The degradation rate observed in the analyses by CRIEPI can be interpreted in terms of the Cr deposited on the three phase boundaries and also of the change in microstructure..
324. K. Kanda, S. Hayashi, F. Takasaki, Z. Noda, S. Taniguchi, Y. Shiratori, A. Hayashi, K. Sasaki, Electrochemical performance of polymer electrolyte fuel cells using carbon-free SnO 2-supported Pt electrocatalysts, 11th Polymer Electrolyte Fuel Cell Symposium, PEFC 11 - 220th ECS Meeting
Polymer Electrolyte Fuel Cells 11
, 10.1149/1.3635766, 2325-2331, 2011.12, [URL], Carbon black is commonly used as an electrocatalyst support material in polymer electrolyte fuel cells (PEFCs). However, during the fuel cell start-stop cycles, carbon is known to be oxidized electrochemically. In the present study, SnO 2 has been selected as a candidate for the support material, and the relation between SnO 2 preparation conditions and electrochemical properties is analyzed..
325. T. Yonekura, Y. Tachikawa, T. Yoshizumi, Y. Shiratori, K. Ito, K. Sasaki, Exchange current density of solid oxide fuel cell electrodes, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570081, 1007-1014, 2011.12, [URL], It is desired to develop computational procedures to simulate internal current density, anode/cathode gas concentrations, and temperature distribution in solid oxide fuel cell (SOFC) systems. In this study, the influences of various operational conditions on the exchange current density, the essential parameter to simulate SOFC performance, are revealed and discussed. The anodic exchange current density depended strongly on the humidity of H 2-based fuel gas, and it exhibited the highest value at around 40% H 2O. The cathodic exchange current density was strongly affected by the operational temperature. Parameters necessary to describe dependencies of exchange current density on various operational parameters were determined by fitting measured exchange current density values with empirical equations..
326. Akari Hayashi, Katsuya Kato, Kazunari Sasaki, Exploration of electrocatalytic reactions in nano-space of carbon materials
Application to fuel cells, 242nd ACS National Meeting and Exposition
ACS National Meeting Book of Abstracts
, 2011.12, With the aim of developing fuel cells for next generation energy technologies, it is necessary to overcome two major problems, cost and durability. In this research, we challenge those problems thought the fundamental development and study of electrode materials in nanometer-scale. To date, we have made carbon materials with ordered 8-nm nano-channels and treated that nano-space as a reaction site. After introduction of catalysts into such nano-space, and resulting materials were applied to the electrode catalysts for fuel cell reactions. In comparison to larger nano-space (over 30 nm), the different phenomena were observed. Both proton and hydrogen/oxygen were effectively provided, and further successful drain of water through the pores was achieved. Due to all these combined conditions, the promotion of electrocatalytic reactions has been accomplished. Based on this characteristic behavior, we are interested in nano-environment around catalysts and will discuss more about that from material design side..
327. K. Sasaki, K. Haga, T. Yoshizumi, D. Minematsu, E. Yuki, R. R. Liu, C. Uryu, T. Oshima, S. Taniguchi, Y. Shiratori, K. Ito, Impurity poisoning of SOFCs, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570280, 2805-2814, 2011.12, [URL], Long-term durability is one of the most important technological issues for SOFC system development. Life time of SOFCs can be critically affected by foreign species, including impurities and minor constituents in fuels and oxidants, from the raw materials of cell components, and from system components. This paper summarizes an effort to understand the impurity poisoning analyzed by adding specific impurity species into fuels under various operational conditions to clarify poisoning mechanisms and their concentration threshold. Possible acceleration procedures for poisoning phenomena have also been discussed..
328. R. R. Liu, S. Taniguchi, Y. Shiratori, K. Ito, K. Sasaki, Influence of SO 2 on the long-term durability of SOFC cathodes, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570221, 2255-2260, 2011.12, [URL], Sulfur poisoning effect on the electrochemical performance and long-term durability of SOFC cathodes has been investigated for (La 0.8Sr 0.2) 0.98MnO 3 (LSM) and La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) up to 1000 hours. Gradual degradation of performance occurred, associated with the formation of strontium sulfate, which depended on SO 2 concentration..
329. T. Yoshizumi, C. Uryu, T. Oshima, Y. Shiratori, K. Ito, K. Sasaki, Sulfur poisoning of SOFCs
Dependence on operational parameters, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting
Solid Oxide Fuel Cells 12, SOFC XII
, 10.1149/1.3570159, 1717-1725, 2011.12, [URL], Sulfur species are major impurities in practical hydrocarbon-based-fuels, chemisorption of which on Ni anode catalysts results in possible performance degradation of SOFC systems. In the present study, degradation of SOFC performance caused by sulfur in prereformed CH 4 has been evaluated under various operational conditions such as current density, fuel utilization, pre-reforming ratio, steam-to-carbon ratio, and operational temperature..
330. Kazunari SASAKI, Kengo HAGA, Tomoo YOSHIZUMI, Dasuke MINEMATSU, Eiji YUKI, Runru LIU, Chie URYU, Toshihiro OSHIMA, Teppei OGURA, Yusuke SHIRATORI, Kohei ITO, Michihisa KOYAMA, Katsumi YOKOMOTO, Chemical Durability of SOFCs: Influence of impurities on long-term performance., J. of Power Sources, 196, 22, 9130-9140, 2011.11.
331. Kazunari Sasaki, Kengo Haga, Tomoo Yoshizumi, Daisuke Minematsu, Eiji Yuki, Runru Liu, Chie Uryu, Toshihiro Oshima, Teppei Ogura, Yusuke Shiratori, Kohei Ito, Michihisa Koyama, Katsumi Yokomoto, Chemical durability of Solid Oxide Fuel Cells
Influence of impurities on long-term performance, Journal of Power Sources, 10.1016/j.jpowsour.2010.09.122, 196, 22, 9130-9140, 2011.11, [URL], Because of the fuel flexibility of Solid Oxide Fuel Cells (SOFCs), various types of fuels may be applied directly or via a simple reforming process, including hydrocarbons, alcohols, coal gas, biogas, besides hydrogen. However, various types of minor constituents in practical fuels and/or from the system components can cause chemical degradation of SOFCs, such as anode and cathode poisoning phenomena. In this study, we compare the influence of various external impurities, including sulfur, chlorine, phosphorus, boron, and siloxane for anodes, and H2O and SO2 for cathodes, on SOFC performance to have a general overview on long-term chemical durability of SOFCs. Chemical compatibility of Ni with foreign species has also been thermochemically considered. Using common model cells, the stability of cell voltage, electrode overpotential, and ohmic loss up to 3000 h has been experimentally examined for H2-based fuels, for hydrocarbon-based fuels, and for partially pre-reformed CH4-based fuels. Increase in degradation rate by impurities was verified for various operational parameters. Impurity poisoning mechanisms are discussed for each specific impurity..
332. Run Ru LIU, Seon Hye KIM, Shunsuke TANIGUCHI, Toshihiro OSHIMA, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Influence of Water Vapor on Long-term Performance and Accelerated Degradation of Solid Oxide Fuel Cell Cathodes., J. Power Sources, http://dx.doi.org/10.1016/j.jpowsour.2010.08.014, 196, 17, 7090-7096, 2011.09.
333. R. R. Liu, S. H. Kim, S. Taniguchi, T. Oshima, Y. Shiratori, K. Ito, K. Sasaki, Influence of water vapor on long-term performance and accelerated degradation of solid oxide fuel cell cathodes, Journal of Power Sources, 10.1016/j.jpowsour.2010.08.014, 196, 17, 7090-7096, 2011.09, [URL], The influence of water vapor in the air on the performance and durability of solid oxide fuel cell (SOFC) has been investigated for the-state-of-the-art cathodes, (La0.8Sr0.2)0.98MnO3 (LSM) and La0.6Sr0.4Co0.2Fe0.8O 3 (LSCF). Durability experiments were carried out at 800 °C up to 1000 h with various water vapor containing-air fed to the cathode side. Both types of cathode materials were basically stable under typical water vapor concentrations in the ambient air. Degradations could be accelerated at much higher water vapor concentrations, which could be associated with the decomposition of the cathode materials. Temperature dependence of this degradation was analyzed between 700 °C and 900 °C under 10 vol% water vapor concentration, which showed that the effect of water vapor depends strongly on the temperature and led to a severe degradation at 700 °C within a short time period for both cathode materials..
334. F. Takasaki, S. Matsuie, Y. Takabatake, Z. Noda, A. Hayashi, Y. Shiratori, K. Ito, K. Sasaki, Carbon-free Pt electrocatalysts supported on SnO2 for polymer electrolyte fuel cells
Electrocatalytic activity and durability, Journal of the Electrochemical Society, 10.1149/1.3625918, 158, 10, B1270-B1275, 2011.08, [URL], The use of SnO2 as an alternative electrocatalyst support improves durability against voltage cycling up to a high potential, corresponding to the start-up and shut-down situation of polymer electrolyte fuel cell (PEFC) systems. Electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity of Pt electrocatalysts as well as electrical conductivity of the electrocatalyst layers increase by doping of SnO2 with Nb or Sb. The durability tests with voltage cycles between 0.9 and 1.3 V versus reversible hydrogen electrode (RHE) potential have revealed that the Pt electrocatalyst supported on SnO2 (Pt/SnO2) withstands 60,000 voltage cycles while maintaining its ECSA, which corresponds to a lifetime of more than 20 years with respect to the durability against voltage cycling. These results indicate that SnO2-supported carbon-free electrocatalysts can be alternatives to the conventional Pt/C electrocatalyst, as a fundamental solution against carbon support corrosion, to improve PEFC durability..
335. Hiromitsu Masuda, Atsushi Yamamoto, Kazunari Sasaki, Sangkun Lee, Kohei Ito, A visualization study on relationship between water-droplet behavior and cell voltage appeared in straight, parallel and serpentine channel pattern cells, Journal of Power Sources, 10.1016/j.jpowsour.2011.02.074, 196, 13, 5377-5385, 2011.07, [URL], It is a critical issue to understand the relationship between water-droplet behavior and cell voltage for the establishment of PEFC water management. We fabricated three cells, whose channel pattern is different: straight one channel, parallel three channels and serpentine one channel. We operated these different channel-pattern cells and visualized water droplets in cathode channel, with systematically changing operation condition to quantitatively compare the performance and water droplet behavior between the cells. Successive process of water behavior, named as flooding, plugging and flushing, emerged in every channel-pattern cell. However, the each channel pattern cell also has inherent water behavior, showing particular cell voltage variation. Within our experimental condition, the serpentine one channel cell showed a superior tolerance to flooding and the highest performance among the three cells..
336. Takahiro YONEKURA, Yuya TACHIKAWA, Tomoo YOSHIZUMI, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Exchange Current Density of Solid Oxide Fuel Cell Electrodes, ECS Transactions, 35, 1, 1007-1014, 2011.05.
337. Tomoo YOSHIZUMI, Chie URYU, Toshihiro OSHIMA, Yusuke SHIRATORI, Kohei ITO, and Kazunari SASAKI, Sulfur Poisoning of SOFCs: Dependence on Operational Parameters., ECS Transactions, 35, 1, 1717-1725, 2011.05.
338. Run Ru LIU, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Influence of SO2 on the Long-term Durability of SOFC Cathodes., ECS Transactions, 35, 1, 2255-2260 , 2011.05.
339. Kazunari SASAKI, Kengo HAGA, Tomoo YOSHIZUMI, Daisuke MINEMATSU, Eiji YUKI, Run Ru LIU, Chie URYU, Toshihiro OSHIMA, Shunsuke TANIGUCHI, Yusuke SHIRATORI, Kohei ITO, Impurity Poisoning of SOFCs., ECS Transactions, 35, 1, 2805-2814, 2011.05.
340. Yusuke SHIRATORI, Tuyen Quang TRAN, Yutaro TAKAHASHI, and Kazunari SASAKI, Application of Biofuels to Solid Oxide Fuel Cell., ECS Transactions, 35, 1, 2641-2651, 2011.05.
341. Kazuya Matsumoto, Tsuyohiko Fujigaya, Kazunari Sasaki, Naotoshi Nakashima, Bottom-up design of carbon nanotube-based electrocatalysts and their application in high temperature operating polymer electrolyte fuel cells, Journal of Materials Chemistry, 10.1039/c0jm02744h, 21, 4, 1187-1190, 2011.01, [URL], We describe the fabrication of a well-defined carbon nanotube (CNT)-based composite, in which the CNTs are individually wrapped by a polymer in a homogeneous fashion and platinum nanoparticles (Pt) are immobilized on the polymer-wrapped CNTs. Polybenzimidazoles (PBIs) are used as the wrapping polymer since a strong adsorption of PBIs onto the CNT surfaces enables the exfoliation of CNT bundles and nanometre-thick PBI wrapping layer serves as a glue for the efficient immobilization of Pt. We demonstrate the use of the composite for the polymer electrolyte fuel cell (PEFC) electrocatalyst. The well-defined interfacial nanostructure of the composite enables efficient reactant diffusion, resulting in good oxygen reduction reaction activity. Single cell tests reveal that the ultra-thin PBI-wrapping layer around the CNTs serves as a proton conducting layer to deliver protons in the catalyst membrane. PEFCs using the composite show an excellent fuel cell performance at 120 °C under non-humid atmosphere, whereas the conventional Nafion-based PEFCs are not workable in such condition. Unique combination of the CNTs and PBIs provides a promising route for the next-generation high temperature PEFC..
342. Sang Kun Lee, Kohei Ito, Kazunari Sasaki, A cross-sectional observation of water behavior in the flow channel in PEFC, 10th Polymer Electrolyte Fuel Cell Symposium, PEFC 10 - 218th ECS Meeting
Polymer Electrolyte Fuel Cells 10, PEFC 10
, 10.1149/1.3484638, 1457-1463, 2010.12, [URL], Liquid water growth pattern in the gas flow channel in PEFC was visualized by using an ex-situ optical cross-sectional observation system developed. We investigated the impact of surface hydrophobicity of the GDL and channel on the liquid water growth pattern. The liquid water, which was emerged at 5 mm back from the gas outlet, was observed with spatial resolution of 20 μm by optimizing the optical system including CCD camera. Pressure drop through the channel was measured to evaluate the impact of water droplet on it. As a result, it is obtained that adhesion force formed in combination of hydrophobic GDL and hydrophilic channel sucked the water from GDL to channel corner, and suppressed the water contact with the GDL surface, and accelerated the water drainage, leading to prevent the water droplet growing in the channel..
343. Kazunari Sasaki, Fumiaki Takasaki, Zhiyun Noda, Shingo Hayashi, Yusuke Shiratori, Kohei Ito, Alternative electrocatalyst support materials for polymer electrolyte fuel cells, 10th Polymer Electrolyte Fuel Cell Symposium, PEFC 10 - 218th ECS Meeting
Polymer Electrolyte Fuel Cells 10, PEFC 10
, 10.1149/1.3484545, 473-482, 2010.12, [URL], Durability of electrocatalysts under severe operational conditions of polymer electrolyte fuel cells (PEFCs) is one of the most important technological issues to be improved. Alternative electrocatalyst support materials are desired, the use of which may solve problems such as oxidation-induced carbon support corrosion. One interesting solution is to use conductive oxide-based catalyst support. We focus our attention to SnO 2, known as an oxide semiconductor with a high electronic conductivity, as a possible electrocatalyst support material. Nanostracture, electrochemical properties and durability of carbon-free electrocatalysts, Pt/SnO2, Pt/Nb-SnO2, Pt/Sb-SnO2, and Pt/Al-SnO2, are investigated. Nano-carbon support materials are also studied as an another option of electrocatalyst support design. Distribution of Pt nanoparticles on such carbon support materials is characterized. Pt electrocatalysts with a diameter of a few nm could be prepared, supported on carbon nanofibers with different structures (including herringbone-type fibers, platelet-type fibers, and highly-conductive vapor-grown fibers) and carbon nanotubes. Technical merits and remaining issues in alternative electrocatalyst support materials selection are discussed..
344. Kazuya MATSUMOTO, Tsuyohiko FUJIGAYA, Kazunari SASAKI and Naotoahi NAKASHIMA, Bottom-up Design of Carbon Nanotube-based Electrocatalysts and their Application in High Temperature Operating Polymer Electrolyte., J. Mater. Chem., 21, 1187-1190, 2010.11.
345. Kazunari SASAKI, Fumiaki TAKASAKI, Zhiyun NODA, Shingo HAYASHI, Yusuke SHIRATORI, Kohei ITO, Alternative Electrocatalyst Support Materials for Polymer Electrolyte Fuel Cells., ECS Transactions, 33(1), pp.473-482, 2010.10.
346. Sang-Kun LEE, Kohei ITO, Kazunari SASAKI, A Cross-sectional Observation of Water Behavior in the Flow Channel in PEFC., ECS Transactions, 33(1), pp.1457-1463, 2010.10.
347. Kengo HAGA,Yusuke SHIRATORI,Yoshihiro NOJIRI,Kohei ITO and Kazunari SASAKI, Phosphorus Poisoning of Ni-Cermet Anodes in Solid Oxide Fuel Cells., J. Electrochem. Soc., 157(11), pp.B1693-B1700, 2010.09.
348. Yusuke SHIRATORI, Takeo IJICHI, Toshihiro OSHIMA and Kazunari SASAKI, Internal Reforming SOFC Running on Biogas., International Journal of Hydrogen Energy, 35(15), pp.7905-7912, 2010.08.
349. Y. Shiratori, T. Ijichi, T. Oshima, K. Sasaki, Internal reforming SOFC running on biogas, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2010.05.064, 35, 15, 7905-7912, 2010.08, [URL], Direct feeding of biogas to SOFC, which is derived from municipal organic wastes, has been investigated as a carbon-neutral renewable energy system. CH4/CO2 ratio in the actual biogas fluctuated between 1.4 and 1.9 indicating biogas composition is strongly affected by the kinds of organic wastes and the operational conditions of methane fermentation. Using anode-supported button cells, stable operation of biogas-fueled SOFC was achieved with the internal reforming mode at 800 °C. Cell voltage above 0.8 V was recorded over 800 h at 200 mA cm-2. It has been revealed that air addition to actual biogas reduced the risk of carbon formation and led to more stable operation without compromising cell voltage due to the lowering of anodic overvoltage..
350. Kazunari SASAKI, Kengo HAGA, Daisuke MINEMATSU, Tomoo YOSHIZUMI, Run Ru LIU, Yusuke SHIRATORI, Kohei ITO, Michihisa KOYAMA and Katsumi YOKOMOTO, Chemical Durability of SOFCs: Influence of Impurities on Long-term Performance., Proceedings of 9th European Solid Oxide Fuel Cell Forum, pp.7-51~7-60, 2010.06.
351. Run Ru LIU, Yusuke SHIRATORI, Toshihiro OSHIMA and Kazunari SASAKI, Water vapor and SO2 poisoning effect on the long-term durability of SOFC cathodes., Proceedings of 9th European Solid Oxide Fuel Cell Forum, pp.7-148~7-155, 2010.06.
352. Yusuke Shiratori, Takeo Ijichi, Toshihiro Oshima, Kazunari Sasaki, Performance of Internal Reforming SOFC Running on Biogas., Proceedings of 9th European Solid Oxide Fuel Cell Forum, pp4-77~4-87, 2010.06.
353. Tomoo YOSHIZUMI, Eiji YUKI, Yusuke SHIRATORI and Kazunari SASAKI, Sulfur Poisoning of SOFCs: Dependence on operational parameters., Proceedings of 9th European Solid Oxide Fuel Cell Forum, pp.7-77~7-85, 2010.06.
354. S. H. Kim, K. B. Shim, C. S. Kim, J. T. Chou, T. Oshima, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Degradation of solid oxide fuel cell cathodes accelerated at a high water vapor concentration, Journal of Fuel Cell Science and Technology, 10.1115/1.3117608, 7, 2, 210111-210116, 2010.04, [URL], The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800° and 1000°. Cell voltage change was negligible at 1000°, while considerable voltage drop was observed at 800° accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La 2O3 formed on the (La0.8Sr02) 0.98MnO3 surface, which is assumed to be the reason for a large voltage drop..
355. K. Haga, Yusuke Shiratori, Y. Nojiri, Kohei Ito, Kazunari Sasaki, Phosphorus poisoning of Ni-cermet anodes in solid oxide fuel cells, Journal of the Electrochemical Society, 10.1149/1.3489265, 157, 11, 2010, [URL], Chemical degradation of anodes in solid oxide fuel cells (SOFCs) induced by phosphorous impurities has been investigated by thermochemical calculations, electrochemical characterization, and microstructural analysis. Thermochemical calculations indicate that Ni phosphides (NimPn) such as Ni5P2 are readily formed under SOFC operational conditions even in the case where the concentration of phosphorous impurities is as low as ppb level. Phosphorous impurities in fuels resulted in the formation of the secondary phase Ni phosphides during operation especially at an operating temperature ∼1000°C. The formation of Ni phosphides and change in anode microstructure were confirmed by using a field-emission-scanning electron microscope coupled with an energy dispersive X-ray analyzer, scanning transmission electron microscope, and X-ray diffraction, leading to the fatal cell performance degradation in the manner that anodic overpotential increased, current incorporation was obstructed, and internal fuel reforming reaction was deactivated..
356. F. Takasaki, Z. Noda, A. Masao, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Carbon-free Pt electrocatalysts supported on doped SnO2 for polymer electrolyte fuel cells, 9th Proton Exchange Membrane Fuel Cell Symposium (PEMFC 9) - 216th Meeting of the Electrochemical Society
ECS Transactions - Proton Exchange Membrane Fuel Cells 9
, 10.1149/1.3210636, 831-837, 2009.12, [URL], Oxidation-induced carbon support corrosion especially in cathode electrocatalysts for polymer electrolyte fuel cells (PEFCs) is one of the important technological issues to be solved. We focus our attention to SnO 2, known as a broad-band oxide semiconductor with a high electronic conductivity, as a possible electrocatalyst support material. In this study, nanostructure, electrochemical properties and durability of carbon-free electrocatalysts, Pt/SnO2, Pt/Nb-SnO2, Pt/Al-SnO 2, are investigated..
357. K. Haga, Y. Shiratori, K. Ito, K. Sasaki, Chemical degradation and poisoning mechanism of cermet anodes in solid oxide fuel cells, 11th International Symposium on Solid Oxide Fuel Cells (SOFC-XI)- 216th ECS Meeting
ECS Transactions - Solid Oxide Fuel Cells 11 (SOFC-XI)
, 10.1149/1.3205748, 2031-2038, 2009.12, [URL], This paper reports the chemical degradation of Ni-based SOFC anodes caused by small amounts of impurities supplied with fuels. In particular, the impurity dependence of degradation behaviors as well as poisoning mechanisms are highlighted and investigated. Poisoning effects by chlorine and siloxanes are found to be critical to achieve satisfactory SOFC durability. In addition, it has also been demonstrated that phosphorus and boron compounds lead to gradual decrease in cell voltage, Ni grain growth, and even formation of nickel phosphates. The measured trends are discussed in relation to the thermochemical calculations and FESEM/STEM-EDX analysis..
358. K. Doumae, T. Usui, T. Yasui, S. Watanabe, T. Oshima, Y. Shiratori, K. Sasaki, Electrochemical properties of NiO-ScSZ anodes prepared from composite precursor containing Ni and Zr, 11th International Symposium on Solid Oxide Fuel Cells (SOFC-XI)- 216th ECS Meeting
ECS Transactions - Solid Oxide Fuel Cells 11 (SOFC-XI)
, 10.1149/1.3205735, 1915-1920, 2009.12, [URL], Generally, cermet anode is produced by mixing nickel oxide with stabilized zirconia. Improvement of the conventional anode is necessary in the viewpoints of electrochemical performance and its productivity. In this study, two approaches were tested in order to enhance the anode performance. First, wet blended Ni-Zr composite hydroxide was applied as a precursor to obtain homogeneous Ni-stabilized zirconia cermet. In the next phase, doping of Mg, Mn and Co to the nickel precursor is performed by co-precipitation method aiming at positive effects of these elements, and electrochemical properties of these anodes are evaluated and compared to those of conventional anode..
359. Yusuke Shiratori, T. Ijichi, T. Oshima, Kazunari Sasaki, Generation of electricity from organic bio-wastes using solid oxide fuel cell, 11th International Symposium on Solid Oxide Fuel Cells (SOFC-XI)- 216th ECS Meeting
ECS Transactions - Solid Oxide Fuel Cells 11 (SOFC-XI)
, 10.1149/1.3205630, 1051-1060, 2009.12, [URL], Direct feeding of biogas to SOFC, which is derived from municipal bio-wastes, has been tested in this research. Because biogas composition is strongly affected by the kind of organic wastes and the operational conditions of methane fermentation, it has been monitored for 100 days using gas Chromatograph in order to reveal the fluctuation of biogas composition and its influence on the SOFC performance. CH4/CO2 ratio in the raw biogas was in the range of 1.4-1.9 and had a tendency to decrease when the cattle dung slurry was fed into the reactor. Using anode-supported button cell, stable operation of direct-biogas SOFC was achieved at 800°C. Cell voltage above 0.8 V was recorded over 350 h at 200 mA cm-2..
360. Kohei Ito, Sangkun Lee, Atsushi Yamamoto, Masaaki Hirano, Hidetaka Muramatsu, Kazunari Sasaki, Kuniyasu Ogawa, In-situ measurement in through-plane direction in PEMFC, 7th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2009
Proceedings of the 7th International Conference on Nanochannels, Microchannels, and Minichannels 2009, ICNMM2009
, 10.1115/ICNMM2009-82132, 1241-1247, 2009.12, [URL], Water management is a large issue for putting PEMFC to practical use. Appropriate water management enables us to suppress the drying in PEM (Polymer Electrolyte Membrane) and the flooding in GDL (Gas Diffusion Layer), which degrade the performance of PEMFC Against the background of importance for the water management, we challenged to develop the measurement method to grasp the water behavior in PEMFC Especially, we focused on through-plane direction measurement, because the through-plane direction in cell has major role for the transport of mass, heat and electric charge in the cell. We developed the three methods to measure the water in cell directly or indirectly: cross sectional cell: micro NMR-sensor array: micro thermocouple array. These three methods successively captured the distribution of the liquid water in GDL, the water content in PEM and the temperature in cell. (Figure Presented) The data obtained help us to give the possible mechanism of how the water in cell impacted the cell voltage..
361. K. Araki, J. Yamamoto, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Performance and long-term durability of nanostructured Ni anodes doped with transition metals prepared by spray mist dryer, 11th International Symposium on Solid Oxide Fuel Cells (SOFC-XI)- 216th ECS Meeting
ECS Transactions - Solid Oxide Fuel Cells 11 (SOFC-XI)
, 10.1149/1.3205749, 2039-2048, 2009.12, [URL], Various additives for Ni anodes mixed with scandium stabilized zirconia (ScSZ) prepared by spray mist dryer are examined for SOFCs in order to improve their anodic activity and long-term durability. Among the additives examined, it is found that the addition of Mn was highly effective to improve anode activity and sulfur tolerance. In case 5 mol% Mn was added to Ni, at 800°C and 200 mA/cm2 for 50% pre-reformed CH4 fuels (S/C = 2.5), the anodic overvoltage was as low as 18 mV and the initial cell voltage drop by 5 ppm H2S was ca. 30 m V, which was less than half of the initial cell voltage drop for undoped Ni-cermet anodes. Mn-oxide reacts with NiO during preparation, while Ni metal nanoparticles will be segregated after reduction and Mn-oxide acts as pinning sites to depress grain growth and agglomeration of Ni particles, leading to lower anodic overvoltage and higher sulfur tolerance. Long-term durability up to 3000 hours has been verified..
362. Sang Kun Lee, Kohei Ito, Kazunari Sasaki, Temperature measurement in through-plane direction in PEFC with a fabricated in-line thermocouple and supporter, 9th Proton Exchange Membrane Fuel Cell Symposium (PEMFC 9) - 216th Meeting of the Electrochemical Society
ECS Transactions - Proton Exchange Membrane Fuel Cells 9
, 10.1149/1.3210599, 495-503, 2009.12, [URL], Temperature distribution in the through-plane direction in polymer electrolyte fuel cell (PEFC) is key information to achieve proper water management. We fabricated an in-line thermocouple of 49 μm diameter, insulated by Parylene coating with 12 μm thickness. The supporter for the thermocouple was fabricated to position the thermocouple to an exact measurement-point in cell, and to protect the thermocouples from the damage during assembling and operating the cell. Seven in-line thermocouples were placed in the cell in array. It was found that the insertion of thermocouples did not cause large decrease of the cell performance. When the current of 0.3 A/cm2 was loaded under the condition of 60 °C separator temperature with supplying H2/Air humidified at 80 % RH, the cathode catalyst layer temperature showed the increase of 1.9 °C and the maximum in the cell..
363. R. R. Liu, S. H. Kim, Yusuke Shiratori, T. Oshima, Kohei Ito, Kazunari Sasaki, The influence of water vapor and SO2 on the durability of solid oxide fuel cells, 11th International Symposium on Solid Oxide Fuel Cells (SOFC-XI)- 216th ECS Meeting
ECS Transactions - Solid Oxide Fuel Cells 11 (SOFC-XI)
, 10.1149/1.3205850, 2859-2866, 2009.12, [URL], The influences of SO2 and water vapor in air were investigated for (La0.8Sr0.2)0.98MnO3 (LSM) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathodes by measuring cell voltage at a constant current density of 200 mA cm-2 and the operational temperature of 800°C. The results of 1000 h durability tests suggest that SO2 and water vapor in the ambient air little affect the performance of both cathode materials under typical operational conditions..
364. Kengo HAGA, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Chemical Degradation and Poisoning Mechanism of Cermet Anodes in Solid Oxide Fuel Cells., ECS Transactions, 25(2), pp.2031-2038, 2009.10.
365. Kenta ARAKI, Junya YAMAMOTO, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Performance and Long-term Durability of Nanostructured Ni Anodes Doped with Transition Metals prepared by Spray Mist Dryer., ECS Transactions, 25(2), pp.2039-2048 , 2009.10.
366. Yusuke SHIRATORI, Takeo IJICHI, Toshihiro OSHIMA and Kazunari SASAKI, Generation of Electricity from Bio-wastes Using Solid Oxide Fuel Cell., ECS Transactions, 25(2), pp.1051-1060 , 2009.10.
367. Kyosuke DOUMAE, Takeshi USUI, Takashi YASUI, Satoshi WATANABE, Toshihiro OSHIMA, Yusuke SHIRATORI and Kazunari SASAKI, Electrochemical Properties of NiO-ScSZ Anodes Prepared from Composite Precursor Containing Ni and Zr., ECS Transactions, 25(2), pp.1915-1920, 2009.10.
368. Runru LIU, Seon Hye KIM, Yusuke SHIRATORI, Toshihiro OSHIMA, Kohei ITO and Kazunari SASAKI, The Influence of Water Vapor and SO2 on the Durability of Solid Oxide Fuel Cells., ECS Transactions, 25(2), pp.2859-2866, 2009.10.
369. Fumiaki TAKASAKI, Akihiro MASAO, Zhiyun NODA, Yusuke SHIRATORI, Kohei ITO and Kazunari SASAKI, Carbon-free Pt Electrocatalysts Supported on SnO2 for Polymer Electolyte Fuel Cells., ECS Transactions, 25(1), pp.831-837, 2009.10.
370. Sangkun LEE, Kohei ITO and Kazunari SASAKI, Temperature Measurement of Through-plane Direction in PEFC with a Fabricated In-line Thermocouple and Supporter., ECS Transactions, 25(1), pp.495-503, 2009.10.
371. Kazunari Sasaki, Kengo Haga, Hydrogen technologies based on fuel cells
Materials and devices, Journal of Japan Institute of Electronics Packaging, 10.5104/jiep.12.505, 12, 6, 505-510, 2009.09, [URL].
372. A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Carbon-free pt electrocatalysts supported on SnO2 for polymer electrolyte fuel cells, Electrochemical and Solid-State Letters, 10.1149/1.3152325, 12, 9, 2009.07, [URL], Carbon-free Pt-based electrocatalysts supported on semiconducting SnO 2 (Pt/ SnO2) have been developed for polymer electrolyte fuel cells (PEFCs) by various electrochemical and microstructural characterizations. Pt/ SnO2 exhibited comparable current-voltage characteristics to conventional Pt electrocatalysts and, in particular, a considerable tolerance against 10,000 cycles of voltages up to 0.9 and 1.3 VRHE (RHE denotes reversible hydrogen electrode) vs the RHE. These results indicate that the carbon-free oxide-supported Pt/ SnO2 can be a promising alternative electrocatalyst with long-term durability against voltage cycling up to higher potentials, as a possible fundamental solution to the PEFC degradation caused by carbon support corrosion..
373. Sang Kun Lee, Kohei Ito, Toshihiro Ohshima, Shiun Noda, Kazunari Sasaki, In situ measurement of temperature distribution across a proton exchange membrane fuel cell, Electrochemical and Solid-State Letters, 10.1149/1.3152331, 12, 9, B126-B130, 2009.07, [URL], The temperature distribution across a proton exchange membrane fuel cell was measured by inserting micro-thermocouples between layers such as a gas diffusion layer and membrane electrode assembly. Under steady-state operation, the cathode catalyst layer had the maximum temperature. The activation overpotential at the cathode catalyst layer served as the main heat source, resulting in the maximum temperature at the cathode catalyst layer. The temperature at the cathode catalyst layer just after the load current was interrupted had the minimum temperature. This is thought to be caused by water evaporation from the cathode catalyst layer, where liquid water accumulates during operation..
374. Yusuke SHIRATORI, Toshihiro OSHIMA, Kazunari SASAKI, Feasibility of Direct-Biogas SOFC, Int. J. of Hydrogen Energy, Vol.33, Iss.21, pp.6316-6321, 2008.11.
375. K. Haga, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Chlorine poisoning of SOFC Ni-cermet anodes, Journal of the Electrochemical Society, 10.1149/1.2980521, 155, 12, 2008.11, [URL], Poisoning effects by chlorine compounds, including Cl2 and HCl, to typical electrolyte-supported solid oxide fuel cells (SOFCs) with Ni-scandia-stabilized zirconia cermet anodes have been evaluated. The degradation rate of cell voltage poisoned by 5 ppm Cl2 was estimated to be ca. 3%1000 h. Chlorine degradation rate increased with increasing Cl 2 concentration. Microstructural change associated with the formation of nickel nanoparticles on zirconia grains, probably via Ni Cl2 (g) sublimation, was observed after 150 h poisoning tests, whereas a partial recovery of cell voltage by removing chlorine from the fuels indicates that the chlorine poisoning is partially reversible. Thermochemical calculations, microstructural analysis, and electrochemical characterizations have revealed that the poisoning phenomena for Ni-based cermet anodes caused by chlorine compounds can be explained by the mixed adsorption-type and sublimation-type poisoning mechanism..
376. Y. Shiratori, T. Oshima, K. Sasaki, Feasibility of direct-biogas SOFC, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2008.07.101, 33, 21, 6316-6321, 2008.11, [URL], Direct feeding of real biogas generated in a methane fermentation reactor to SOFC was tested by using Ni-ScSZ cermet as an anode material. At the operating temperature of 1000°C, cell voltage above 0.9V (at 200 mA cm -2) was stably obtained over 50h without carbon deposition showing direct-biogas SOFC is feasible. This system is environmental-friendly, compact and cost-effective energy conversion system in which internal dry reforming of CH4 proceeds on Ni-based anode using CO2 included in biogas without external reformer and precious metal catalyst. H2S poisoning test was performed simulating H2S contamination of biogas. Electrochemical and catalytic properties of Ni-ScSZ anode in feeding simulated biogas mixture (CH4/CO2 = 1.5) and their changes by H 2S supply were measured at 1000°C under 200 mA cm-2. 1 ppm H2S poisoning caused about 9% voltage drop and about 40% decrease in reaction rate of internal reforming, however, stable operation was achieved and complete recovery of cell voltage and reaction rate after stopping the H2S supply was confirmed, indicating that direct-biogas SOFC operated at 1000°C is tolerant to 1 ppm level H2S contamination..
377. Jyh-Tyng CHOU, Kazunari SASAKI, Microstructural Analysis of Catalyst/Catalyst Support Interfaces of PEFC Electrocatalysts, Solid State Ionics, Vol.179, Iss.27-32, pp.1405-1408, 2008.09.
378. Kengo HAGA, Yusuke SHIRATORI, Kohei ITO, Kazunari SASAKI, Chlorine Poisoning of SOFC Ni-Cermet Anodes, J. Electrochem. Soc., Vol.155, Iss.12, pp. B1233-B1239, 2008.09.
379. Seon Hye Kim, Toshihiro Ohshima, Yusuke Shiratori, Kohei Itoh, Kazunari Sasaki, Effect of water vapor and SOx in air on the cathodes of solid oxide fuel cells, Life-Cycle Analysis for New Energy Conversion and Storage Systems
Proceedings - CIS Workshops 2007, 2007 International Conference on Computational Intelligence and Security Workshops, CISW 2007
, 131-137, 2008.09, The influence of chemical species, water vapor and SOx, included in air on the voltage drop of SOFCs was studied. La2O3 was formed on the surface of cathode and caused the significant voltage drop of cells under high water vapor concentrations at 800°. The voltage drop of cells also occurred with SO2 in air but was recovered with supplying SO 2-free air into the cells. It was considered that the cell voltage drop caused by SOx was due to the adsorption of sulfur and/or the formation of sulfur compounds on the surface of cathodes..
380. J. T. Chou, Kazunari Sasaki, Microstructural analysis of catalyst/catalyst support interfaces of PEFC electrocatalysts, Solid State Ionics, 10.1016/j.ssi.2008.04.011, 179, 27-32, 1405-1408, 2008.09, [URL], In this study, we observed the catalyst/catalyst support interfaces of Polymer Electrolyte Fuel Cell (PEFC) electrocatalysts by High-Resolution TEM. As the catalyst supports, various carbon nanofibers, including VGCF (Vapor-grown carbon fibers), Platelet type carbon nanofibers and Herringbone-type carbon nanofibers, were applied. We found larger Platinum particles in the Pt/VGCF. The interfacial structure was identified to be the (111)Pt//(0001)Graphite, so that its boundary is relatively stable, whereas particle growth could easily occur. On the contrary, in the Pt/Platelet and in the Pt/Herringbone, well-dispersed Platinum particles were observed, as the catalyst/catalyst support interface is rather unstable. Moreover, twin was observed in the Platinum particles supported on the Herringbone-type nanofibers..
381. K. Haga, S. Adachi, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Poisoning of SOFC anodes by various fuel impurities, Solid State Ionics, 10.1016/j.ssi.2008.02.062, 179, 27-32, 1427-1431, 2008.09, [URL], Poisoning effects by various fuel impurities, including H2S, CH3SH, COS, Cl2, and siloxane, to Ni-ScSZ cermet anodes have been analyzed and compared. Degradation of cell performance caused by these impurities was characterized by measuring cell voltage and anode polarization at a constant current density of 0.2 Acm- 2 for humidified H2 and CH4 fuels. Poisoning for hydrogen-based fuels containing 5 ppm sulfur compounds, H2S, CH3SH, and COS, caused an initial cell voltage drop of about 15 mV at 1000 °C. The initial voltage drop was independent of the kind of sulfur compounds, whereas in the case of poisoning by CH3SH, an additional gradual decrease in cell voltage was clearly detected after the initial voltage drop. Thermochemical calculation and FESEM-EDX analysis also indicated that the poisoning by Cl2 caused the formation of nickel nano-particles on zirconia grains via NiCl2 (g), while the poisoning by siloxane formed segregated silica (SiO2) in porous cermet anodes..
382. Kazunari Sasaki, Thermochemical stability of sulfur compounds in fuel cell gases related to fuel impurity poisoning, Journal of Fuel Cell Science and Technology, 10.1115/1.2930769, 5, 3, 2008.08, [URL], Since sulfur compounds are the major poisons of fuel cell systems, equilibrium concentrations of minor sulfur-based impurities in fuel cell fuels are thermochemically calculated in the temperature range between 400°C and 1000°C. As sulfur-based impurities in fuel cell gases, H2S(g), elementary sulfur, inorganic sulfur compounds, mercaptans, alkyl (di-)sulfides, thiophenes, and related compounds have been taken into account. Various types of fuels are also considered, including H2, H2,-CO, CO, CH4, biogas, liquidified petroleum gas, gasoline, kerosene, and diesel fuel. Among the 21 kinds of sulfur-based typical impurities considered, H2S(g) is the most stable sulfur-based species. COS(g) can also coexist, but even in CO-rich gases and in hydrocarbon-based fuels, COS concentration in equilibrium is one order or a few orders of magnitude lower than H2S concentration. Other sulfur compounds, such as CH4S(g) at intermediate temperatures and HS(g) and SO2(g) at high temperatures, are also expected to coexist but their concentrations are less than 1 ppb (parts per billion) assuming thermochemical equilibrium..
383. Kazunari Sasaki, Kengo Haga, Junya Yamamoto, Kaori Dobuchi, Impurity Poisoning of SOFCs: Towards Understanding Chemical Degradation Mechanisms, Proceedings of the 8th European Solid Oxide Fuel Cell Forum, B1003, 2008.07.
384. Yusuke Shiratori, Kazunari Sasaki, NiO-ScSZ and Ni0.9Mg0.1O-ScSZ-based anodes under internal dry reforming of simulated biogas mixtures, Journal of Power Sources, 10.1016/j.jpowsour.2008.03.001, 180, 2, 738-741, 2008.06, [URL], Solid oxide fuel cells (SOFCs) with NiO-ScSZ and Ni0.9Mg0.1O-ScSZ-based anodes were operated by directly feeding a fuel mixture of CH4, CO2 and N2 (CH4 to CO2 ratio of 3:2). Stable operation under constant current load (200 mA cm-2) was achieved with a NiO-ScSZ type anode during 200 h operating hours at 900 °C. Less stable operation occurred with a Ni0.9Mg0.1O-ScSZ type anode. In the case of SOFC with Ni0.9Mg0.1O-ScSZ as the anode, the methane reforming activity was higher than that with NiO-ScSZ. This was explained by change in the microstructure promoting reforming reactions. However, the addition of MgO resulted in degradation of electrochemical performance due to increase in ohmic resistance of the anode material during operation..
385. S.H. Kim, T. Ohshima, Y. Shiratori, K. Ito, K. Sasaki, Effect of water vapor and SOx in air on the cathodes of solid oxide fuel cells, Materials Research Society Symposium Proceedings, 1041, pp. 131-137, 2008.04.
386. Hiromitsu Masuda, Kohei Ito, Toshihiro Oshima, Kazunari Sasaki, Comparison between numerical simulation and visualization experiment on water behavior in single straight flow channel polymer electrolyte fuel cells, Journal of Power Sources, 10.1016/j.jpowsour.2007.11.069, 177, 2, 303-313, 2008.03, [URL], A relationship between a flooding and a cell voltage drop for polymer electrolyte fuel cell was investigated experimentally and numerically. A visualization cell, which has single straight gas flow channel (GFC) and observation window, was fabricated to visualize the flooding in GFC. We ran the cell with changing operation condition, and measured the time evolution of cell voltage and took the images of cathode GFC. Considering the operation condition, we executed a developed numerical simulation, which is based on multiphase mixture model with a formulation on water transport through the surface of polymer electrolyte membrane and the interface of gas diffusion layer/GFC. As a result in experiment, we found that the cell voltage decreased with time and this decrease was accelerated by larger current and smaller air flow rate. Our simulation succeeded to demonstrate this trend of cell voltage. In experiment, we also found that the water flushing in GFC caused an immediate voltage change, resulting in voltage recovery or electricity generation stop. Although our simulation could not replicate this immediate voltage change, the supersaturated area obtained by our simulation well corresponded to fogging area appeared on the window surface in the GFC..
387. Kohei Ito, Kensuke Ashikaga, Hiromitsu Masuda, Toshihiro Oshima, Yasushi Kakimoto, Kazunari Sasaki, Estimation of flooding in PEMFC gas diffusion layer by differential pressure measurement, Journal of Power Sources, 10.1016/j.jpowsour.2007.10.019, 175, 2, 732-738, 2008.01, [URL], The flooding, especially in gas diffusion layer (GDL), is one of the critical issues to put PEMFC to practical use. However, the experimental data of the flooding in GDL is so insufficient that the optimization design related to the water management for GDL has not established. In this study we developed a method to estimate the water saturation, namely the ratio of liquid water to pore volume in GDL. We fabricated a simple interdigitated cell where the supply gas is enforced to flow under rib. This structure enables to estimate the liquid water ratio in GDL by the measurement of differential pressure through the cell. We operated the cell and measured the differential pressure, and succeeded in estimating the water saturation, which changed largely with changing cell operation condition. In addition to this deferential pressure measurement, we measured the ionic resistance in polymer electrolyte membrane by ac impedance method. We evaluated and discussed the influence of the water saturation on cell voltage..
388. K. Sasaki, S. Adachi, K. Haga, M. Uchikawa, J. Yamamoto, A. Iyoshi, J. T. Chou, Y. Shiratori, K. Itoh, Fuel impurity tolerance of solid oxide fuel cells, 10th International Symposium on Solid Oxide Fuel Cells, SOFC-X
ECS Transactions - 10th International Symposium on Solid Oxide Fuel Cells, SOFC-X
, 10.1149/1.2729277, 1675-1683, 2007.12, [URL], While SOFCs are the most flexible fuel cells with respect to fuel selection, fuel impurities in practical SOFC fuels can cause degradation of electrodes and thus electrochemical performance. The understanding of fuel impurity poisoning and the increase in tolerance are therefore of technological relevance for SOFC commercialization. Along with thermochemical calculations on the stability of typical fuel impurities under SOFC operational conditions, fuel impurity poisoning of SOFCs is analyzed by using various impurity-containing fuel gases with respect to operational temperature, type and concentration of impurities, fuel composition, and steam-to-carbon ratio. We have revealed that poisoning depends on operational conditions and types of fuels and impurities. The poisoning effect becomes significant for internal-reforming SOFCs operated with humidified methane-based fuels. Poisoning mechanisms are discussed, based on cell voltage and durability data..
389. Y. Shiratori, K. Sasaki, Microstructure and electrochemical properties of Ni1-xMg xO-ScSZ cermet anodes for biogas fueled SOFCs, 10th International Symposium on Solid Oxide Fuel Cells, SOFC-X
ECS Transactions - 10th International Symposium on Solid Oxide Fuel Cells, SOFC-X
, 10.1149/1.2729280, 1701-1710, 2007.12, [URL], To enhance catalytic activity for internal reforming of hydrocarbon-fuels, catalyst based on Ni1-xMgxO was prepared. Small particles of Ni, ca. 50-100 nm in size, were formed by the reduction of the mixed oxide, whereas Ni particles formed from NiO easily agglomerated resulting in smaller catalyst area in the cermet anodes. Ni1-xMgxO-ScSZ anode was fabricated and applied to biogas-fueled SOFC In using Ni 0 9Mg0 1O-ScSZ, cell voltages of about 850 and 950 mV for humidified and dry biogases, respectively, were achieved at 900°C in 50 h operation under constant current density of 200 mA cm-2..
390. Y. Kawasoe, S. Tanaka, T. Kuroki, H. Kusaba, K. Ito, Y. Teraoka, K. Sasaki, Preparation and electrochemical activities of Pt-Ti alloy PEFC electrocatalysts, Journal of the Electrochemical Society, 10.1149/1.2756369, 154, 9, B969-B975, 2007.08, [URL], Titanium is one of the most stable materials, remaining undissolved under strongly acidic polymer electrolyte fuel cell (PEFC) conditions. Nanocrystalline Pt-Ti alloy electrocatalysts with a catalyst grain size of several nanometers have been successfully prepared by the colloidal and sol-gel method, characterized by X-ray diffraction, field-emission scanning electron microscope, scanning transmission electron microscope, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. Electrochemical activities were evaluated by current-voltage characteristics measurements using membrane electrode assemblies for humidified H2 fuels with or without 100 ppm CO, cyclic voltammetry, and CO -stripping voltammetry in 0.1 M HClO4. Pt-Ti alloy electrocatalysts exhibited higher electrochemical performance than pure Pt catalyst, i.e., higher activity for oxygen reduction reactions and improved CO tolerance..
391. R. Karita, H. Kusaba, K. Sasaki, Y. Teraoka, Superiority of nitrate decomposition method for synthesis of K2NiF4-type LaxSr2-xMnO4 catalysts, Catalysis Today, 10.1016/j.cattod.2007.06.023, 126, 3-4 SPEC. ISS., 471-475, 2007.08, [URL], K2NiF4-type La0.2Sr1.8MnO4 was synthesized by nitrate (ND) and nitrate/acetate (NAD) decomposition methods as well as solid-state reaction. Single-phase oxide was obtained at 550 °C by the ND method just after the decomposition of Sr(NO3)2 and at 1000 °C by the NAD method after the decomposition of SrCO3. The K2NiF4-type oxide was hardly formed by the solid-state reaction. In the La-Sr-Mn system, an intermediate compound of SrCO3, if present or formed during the decomposition process, interfered with the low-temperature formation of the K2NiF4-type oxide because of its high decomposition temperature about 1000 °C. The ND method used only metal nitrates and no starting materials with carbon source, so that the low-temperature synthesis of the K2NiF4-type oxide was realized without forming obstinate intermediate compound of SrCO3. The low-temperature synthesis was possible for LaxSr2-xMnO4 with the substitution of La (0 < x < 0.5) and not for La0.2A1.8MnO4 (A = Ca and Ba). The effect of A-site cations on the K2NiF4-phase formation was discussed from the geometric aspect..
392. Y. Kawasoe, S. Tanaka, T. Kuroki, H. Kusaba, K. Ito, Y. Teraoka, and K. Sasaki, Preparation and Electrochemical Activities of Pt–Ti Alloy PEFC Electrocatalysts, J. Electrochem. Soc., 154[9] B969-B975 (2007), 2007.07.
393. 伊藤衡平、足利謙介、柿本益志、大嶋敏宏、益田啓光、佐々木一成, 差圧計測を介したPEMFCガス拡散層における水詰りの推算, 日本機械学会論文集B編, 073巻731号、pp.1556-1561, 2007.07.
394. Kohei Ito, Kensuke Ashikaga, Yasushi Kakimoto, Toshihiro Oshima, Hiromitsu Masuda, Kazunari Sasaki, Estimation of flooding in PEMFC gas diffusion layer by differential pressure measurement, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 73, 7, 1556-1561, 2007.07, The flooding, especially in gas diffusion layer (GDL), is one of the critical issues to put PEMFC to practical use. However, the experimental data of the flooding in GDL is so insufficient that the optimization design to solve the flooding problem in GDL has not established until now. In this study we show a method to estimate the water saturation, namely the liquid water ratio for unit volume in GDL. We fabricated a simple interdigitated cell where the supply gas is enforced to flow under rib. This structure made it possible to capture the water droplet in GDL with the measurement of differential pressure through the cell. We operated the cell and measured the differential pressure, and succeeded in estimating the water saturation, which largely changed with changing cell operation condition. In addition to deferential pressure measurement, we measured the ionic resistance in polymer electrolyte membrane by AC impedance method. We evaluated the effect of the water saturation on the decrease of cell voltage..
395. Y. Shiratori, K. Sasaki, Microstructure and Electrochemical Properties of Ni1-xMgxO-ScSZ Cermet Anodes for Biogas Fueled SOFCs, Solid Oxide Fuel Cells 10 (SOFC-X), ECS Transactions, 7(1),pp.1701-1710, 2007.06.
396. K. Sasaki, S. Adachi, K. Haga, M. Uchikawa, J. Yamamoto, A. Iyoshi, J. -T. Chou, Y. Shiratori, K. Itoh, Fuel Impurity Tolerance of Solid Oxide Fuel Cells, Solid Oxide Fuel Cells 10 (SOFC-X), ECS Transactions, 7(1),pp.1675-1683, 2007.06.
397. Hiromitsu Masuda, Kohei Ito, Yasushi Kakimoto, Kazunari Sasaki, Numerical analysis of transient response in polymer electrolyte membrane fuel cell considering gas/liquid two phase flow, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 73, 3, 855-862, 2007.03, It is important to elucidate the transient characteristics of polymer electrolyte membrane fuel cell (PEMFC), because it may be operated at a wide range of loads, and may have frequent starts and stops. In these unsteady conditions, the water management problem such as the flooding in cell and the drying of proton exchange membrane (PEM) tends to occur and degrades the performance of PEMFC. Based on these issues, a two dimensional, two-phase and transient numerical simulator for unit-PEMFC has been developed to study the transient characteristics of PEMFC. As for the gas/ liquid two-phase flow formulation in GDL. multiphase mixture model have been employed. In this study, we derived four time constants, which characterize the transient response of PEMFC. In addition, we numerically simulated the transient response of PEMFC to step-wise change of load current from 0.5 to 1.0 A/cm2 and succeeded to explain the transient response of cell voltage ( Vcell) by the four time constants. The results show that, just after the change of current, Vcell decreases by IR resistance in a moment, and then decreases in 10-1 s time-scale by the re-distribution of oxygen gas and by the charge of electric double layer capacitor. Then Vcell increases slightly in 101 s time-scale by wetting of PEM. Finally, V cell decreases again in 102 s time-scale by the development of liquid saturation in GDL..
398. R. Karita, H. Kusaba, K. Sasaki, Y. Teraoka, Synthesis, characterization and catalytic activity for NO-CO reaction of Pd-(La, Sr)2MnO4 system, Catalysis Today, 10.1016/j.cattod.2006.08.028, 119, 1-4, 83-87, 2007.01, [URL], LaxSr2-xMnO4 (0 ≤ x ≤ 0.8) oxides were synthesized and single-phase K2NiF4-type oxides were obtained in the range of 0.1 ≤ x < 0.5. The catalytic activity of LaxSr2-xMnO4 for NO-CO reaction increased with increasing x in the range of solubility limit of La. La0.5Sr1.5MnO4 showed the highest activity among LaxSr2-xMnO4 prepared in this study, but its activity was inferior to perovskite-type La0.5Sr0.5MnO3. Among the Pd-loaded catalysts, however, Pd/La0.8Sr1.2MnO4 showed the higher activity and the selectivity to N2 than Pd/La0.5Sr0.5MnO3 and Pd/γ-Al2O3. The excellent catalytic performance of Pd/La0.2Sr1.2MnO4 could be ascribable to the formation of SrPd3O4 which was detected by XRD in the catalyst but not in the other two catalysts..
399. Kohei Ito, Hiroki Ohshima, Yoshiyuki Oie, Kensuke Ashikaga, Yasushi Kakimoto, Kazunari Sasaki, Tomohiko Miyazaki, Hiromitsu Masuda, Estimation of flooding in PEMFC gas diffusion layer by differential pressure measurement, 4th International ASME Conference on Fuel Cell Science, Engineering and Technology, FUELCELL2006
Proceedings of 4th International ASME Conference on Fuel Cell Science, Engineering and Technology, FUELCELL2006
, 2006.12, The flooding, especially in gas diffusion layer (GDL), is one of the critical issues to put PEMFC to practical use. However, the experimental data of the flooding in GDL is so insufficient that the optimization design to solve the flooding problem in GDL has not established until now. In this study we show a method to estimate the water saturation, namely the water droplet occupation for unit volume in GDL. We fabricated a simple interdigitated cell where the supply gas is enforced to flow under rib. This structure made it possible to capture the water droplet in GDL with the measurement of differential pressure through the cell. We operated the cell and measured the differential pressure, and estimated the water saturation with assuming that the flow in GDL is Darcy flow and that the GDL can be treated as sphere packed bed. In addition to deferential pressure measurement, we measured the ionic resistance in polymer electrolyte membrane by AC impedance method. We evaluated the effect of the water saturation on the decrease of cell voltage..
400. Hiromitsu Masuda, Tomohiko Miyazaki, Kohei Ito, Kensuke Ashikaga, Yasuyuki Kakimoto, Kazunari Sasaki, Numerical simulation of two-phase flow and transient response in polymer electrolyte fuel cell, 4th International ASME Conference on Fuel Cell Science, Engineering and Technology, FUELCELL2006
Proceedings of 4th International ASME Conference on Fuel Cell Science, Engineering and Technology, FUELCELL2006
, 2006.12, It is important to elucidate the transient characteristics of polymer electrolyte fuel cells (PEFC), especially when PEFC is applied to relatively small-scale power applications where it will be subjected to a wide range of loads, and may have frequent starts and stops. In addition, the water management problem, which is represented by flooding in cell and drying in proton exchange membrane (PEM), is another issue to address. The flooding is caused by liquid water accumulated in GDL and/or flow channel; the liquid water hinders mass transfer of gases to and from active layers; it can lead to rapid deterioration of cell performance. And the water management relates to the transient response of PEFC frequently. Based on these issues we wrote a numerical simulation program for unit-PEFC, which can simulate the successive events of vapor condensation, liquid saturation growth, corresponding to the dynamic change of cell voltage. We formulated mass, momentum and energy conservation equation with equivalent electric circuit; we discretized and numerically solved them. As for the gas/liquid two-phase flow formulation in GDL, we utilized multi-phase mixture (M2) model. As for the multi-component diffusion formulation, we utilized Stefan-Maxwell equation. Using the program, we simulated the transient response to rapid increase of load current. When the current density changed from 0.5 A/cm2 to 1.0 A/cm2 instantaneously, cell voltage (Vcell) changed in the following manner. Just after the change of current, Vcell decreased instantaneously corresponding to IR resistance and decreased again in 10-1s time-scale with the re-distribution of oxygen and with the charge of electric double layer capacitor. Then Vcell increased slightly in 101s time-scale with PEM wetting. Finally, Vcell decreased in 10 2-103 s time-scale with the development of liquid saturation in GDL..
401. Y. Teraoka, H. Shimokawa, Ch Y. Kang, H. Kusaba, K. Sasaki, Fe-based perovskite-type oxides as excellent oxygen-permeable and reduction-tolerant materials, Solid State Ionics, 10.1016/j.ssi.2006.05.037, 177, 26-32 SPEC. ISS., 2245-2248, 2006.10, [URL], Development of new mixed conductors with both high oxygen permeability and phase stability under reducing atmosphere is indispensable for realizing practical MIEC systems of oxygen separation and membrane reactor. In this study, a family of Co-free Fe-based perovskite-type oxides, (Ba,Sr)(Fe,Mn)O3-δ was prepared and their oxygen permeability and phase stability against reduction were examined. Optimum Ba doping concentration at A site was found around 30%, and Ba0.3Sr0.7FeO3-δ showed highest oxygen permeability (3.0 cm3(STP)cm- 2 min- 1 at 900 °C) in this study. Perovskite-type oxides of the Ba-Mn-Fe-O and Ba-Sr-Mn-Fe-O systems with appropriate compositions preserved the structure even after annealing in the reducing atmosphere of 5% H2/N2 at 1000 °C, showing their exceeding reduction tolerance..
402. Kazunari Sasaki, K. Susuki, A. Iyoshi, M. Uchimura, N. Imamura, H. Kusaba, Y. Teraoka, H. Fuchino, K. Tsujimoto, Y. Uchida, N. Jingo, H 2S poisoning of solid oxide fuel cells, Journal of the Electrochemical Society, 10.1149/1.2336075, 153, 11, 2006.10, [URL], The influence of H2 S fuel impurity on power generation characteristics of solid oxide fuel cells (SOFCs) has been analyzed by measuring cell voltage at a constant current density, as a function of H2 S concentration, operational temperature, and fuel gas composition. Reversible cell voltage change was observed around 1000°C, while fatal irreversible degradation occurred at a lower operational temperature, at a higher H2 S concentration, and at a lower fuel H2 CO ratio. Sulfur tolerance of SOFCs was improved by using Sc2 O3 -doped Zr O2 instead of Y2 O3 -doped Zr O2 as electrolyte and/or as electrolyte component in the anode cermets. It has been found that H2 S poisoning consists of at least two stages, i.e., an initial cell voltage drop within a short time period to a metastable cell voltage, followed by a gradual larger cell voltage drop. Possible H2 S poisoning processes are discussed..
403. CH Y. Kang, H. Kusaba, H. Yahiro, Kazunari Sasaki, Y. Teraoka, Preparation, characterization and electrical property of Mn-doped ceria-based oxides, Solid State Ionics, 10.1016/j.ssi.2006.04.016, 177, 19-25 SPEC. ISS., 1799-1802, 2006.10, [URL], Manganese-doped ceria-based oxides, Ce1-xMnxO2-δ (0.05 ≤ x ≤ 0.3) and Ce1-x-yGdxMnyO2-δ ̇ (0.05 ≤ x≤ 0.2, 0.05 ≤ y ≤ 0.25) were synthesized, and crystal phase analysis by XRD and measurements of electrical properties were performed. Solubility limit of Mn in Ce1-xMnxO2-δ ̇ seemed to be between 5 mol% and 10 mol% and Mn3O4 was the main by-product above the solubility limit in the case of heat treatment at 1300 °C. Judging from the oxygen partial pressure dependence of total conductivity and emf measurements, Ce1-xMnxO2-δ ̇ is a single-phase mixed conductor within the composition below the solubility limit, and when the composition of Mn exceeds the solubility limit, it becomes the dual-phase mixed conductor of Ce1-xMnxO2-δ ̇ and Mn3O4. The doing of Mn in gadlia-doped ceria, Ce1-x-yGdxMnyO2-δ ̇ (0.05 ≤ x ≤ 0.2, 0.05 ≤ y ≤ 0.25), was more difficult than that in CeO2 presumably due to the preferential reaction between Gd and Mn to give GdMnO3 to the GDC solid solution formation, and the Mn doping seems not to be so effective in preparing the mixed ionic-electronic conductor based on GDC..
404. H. Kusaba, Y. Shibata, K. Sasaki, Y. Teraoka, Surface effect on oxygen permeation through dense membrane of mixed-conductive LSCF perovskite-type oxide, Solid State Ionics, 10.1016/j.ssi.2006.05.038, 177, 26-32 SPEC. ISS., 2249-2253, 2006.10, [URL], La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991) dense disks with different thicknesses and surface areas were prepared to investigate the contribution of surface reactions and bulk diffusion in oxygen permeation phenomena. The bulk diffusion controlled situation became significant with increasing the membrane thickness, and the surface reaction controlled situation prevailed at smaller surface area. The increase in surface area at the low P(O2) (anode) side was more effective to increase the oxygen permeation flux than that at the high P(O2) (cathode) side. The coating of a porous catalyst layer below the optimum thickness was also effective in enhancing the oxygen permeability due to the increase in surface area, but the coating with too thick layer deteriorated the permeability probably due to the increase in the gas diffusion resistance..
405. Kazunari Sasaki, Katsushi Susuki, Akira Iyoshi, Shuichi Adachi, Masanobu Uchimura, Naofumi Imamura, Yusuke Shiratori, Hajime Kusaba, Yasutake Teraoka, Fuel Impurity Tolerance of Solid Oxide Fuel Cells, Proceedings of 7th European SOFC Forum, pp.49, 2006.07.
406. Yusuke Shiratori, Yasutake Teraoka, Kazunari Sasaki, Ni1-x-yMgxAlyO-ScSZ cermet anodes for biogas-fueled SOFCs, Proceedings of 7th European SOFC Forum, pp.94, 2006.07.
407. Kohei ITO, Hiromitsu MASUDA, Tomohiko MIYAZAKI, Yasushi KAKIMOTO, Kensuke ASHIKAGA, Kazunari SASAKI, Estimation of Flooding in PEMFC Gas Diffusion Layer by Differential Pressure Measurement, The 4th International Conference on Fuel Cell Science, Engineering and Technology, 2006.06.
408. Hiromitsu MASUDA, Kohei ITO, Yasushi KAKIMOTO, Tomohiko MIYAZAKI, Kensuke ASHIKAGA, Kazunari SASAKI, Numerical Simulation of Two-Phase Flow and Transient Response in Polymer Electrolyte Fuel Cell, The 4th International Conference on Fuel Cell Science, Engineering and Technology, 2006.06.
409. Y. Shiratori, Y. Teraoka, K. Sasaki, Ni1-x-yMgxAlyO-ScSZ anodes for solid oxide fuel cells, Solid State Ionics, 10.1016/j.ssi.2006.06.010, 177, 15-16, 1371-1380, 2006.06, [URL], Three types of cermets based on NiO-ScSZ (A), Ni0.9Mg0.1O-ScSZ (AMg) and Ni0.9Mg0.095Al0.005O-ScSZ (AMgAl) were applied as SOFC anodes. Humidified H2 and simulated biogas (CH4:CO2 = 6:4) were directly supplied to the anode side of SOFC single cell. Catalytic activities for the reforming and the electrochemical reactions were tested in a typical electrochemical measurement setup. When hydrogen (3% H2O) was supplied as a fuel, the three anodes showed almost the same voltage losses (anodic overvoltages) of ca. 40 mV at 400 mA cm- 2 at 1000 °C. However, supplying the simulated biogas, AMg and AMgAl showed smaller losses of 25 and 29 mV, respectively, than those in supplying hydrogen, whereas A showed the loss of more than 40 mV. Through this study, it was revealed that when the biogas is selected as a fuel, the electrochemical efficiency of the internal reforming SOFC is enhanced by using AMg or AMgAl as anode materials instead of A. Although the higher performances of AMg and AMgAl mainly result from the stability of small Ni particles against sintering, in addition to this effect, basic (Ni,Mg)O solid solution or MgO existing in the electrocatalysts contributes to further activity enhancement..
410. Yasutake Teraoka, Hironobu Shimokawa, Hajime Kusaba, Kazunari Sasaki, Fe/Mn-based perovskite-type oxides with excellent oxygen permeability and reduction tolerance, Solid State Ionics - 2004
Materials Research Society Symposium Proceedings
, 835, 77-83, 2005.06, A family of Co-free, Fe/Mn-based perovskite-type oxides, (Sr, A′)(Fe, Mn)O3-δ (A′=La, Ba, Ca), was synthesized, and their oxygen permeability and phase stability in reducing atmosphere were investigated. The substitution of Mn at B site caused the decrease in oxygen permeability. As for the effect of A-site substitution, prominent promotion was observed by the substitution of Ba for 30% of Sr, and Ba0.3Sr 0.7FeO3-δ was found to be one of most excellent oxygen permeable materials with the permeation flux of 3.0 cm3(STP) cm-2 min-1 at 900°C. Reduction tolerance was evaluated by TG measurements in a 5%H2/N2 stream up to 1000°C. After the TG measurements, crystal structures of La-Sr-Co-Fe-O and Sr-Fe-(Mn)-O perovskites were decomposed or transformed into low oxygen permeable phases, but the perovskite-type structure of Ba-Sr-Fe-(Mn)-O survived. The Fe/Mn-based perovskites with high oxygen permeability and exceeding reduction tolerance could be used as stable membrane materials for membrane reactors catalyzing NO-CH4 reaction and the partial oxidation of CR4 into synthesis gas..
411. Kazunari Sasaki, Kenji Shinya, Shuhei Tanaka, Yuudai Kawazoe, Takashi Kuroki, Kouhei Takata, Hajime Kusaba, Yasutake Teraoka, Nanostructured PEFC electrode catalysts prepared via in-situ colloidal impregnation, Unknown Journal, 835, 241-246, 2005, Nanostructured Platinum-based electrode catalysts were prepared via in-situ colloidal impregnation for polymer electrolyte fuel cells. Crystallite size, grain size, and distribution of Pt nanoparticles on carbon support materials were characterized by XRD, TEM, high-resolution FESEM, and STEM. Effective surface area and kinetically-controlled current density of Pt electrode catalysts were analyzed by cyclic and hydrodynamic voltammetry using rotating disk electrodes. PEFCs with these electrode catalysts were also prepared and their I-V characteristics were examined at 80°C. We have succeeded to develop Pt electrode catalysts with a diameter of a few nm, supported on carbon nanofibers with different structures (including herringbone-type fibers, platelet-type fibers, and highly-conductive vapor-grown fibers), carbon nanotubes, as well as carbon black. The dependencies of nanostructure and electrochemical properties on crystallographic structure of carbon support materials and preparation conditions of electrode catalysts are analyzed and discussed. Nanostructural design of PEFC electrode catalyst layers using carbon nanofibers as catalyst supports and electrode fillers is also discussed..
412. Kazunari Sasaki, K. Shinya, S. Tanaka, A. Furukawa, K. Ando, T. Kuroki, H. Kusaba, Y. Teraoka, Nanostructuring of PEFC electrode catalysts using carbon nanofibers, 206th Meeting of The Electrochemical Society Fall 2004
Proton Conducting Membrane Fuel Cells IV - Proceedings of the International Symposium
, 159-170, 2004.12, Electrode catalysts of polymer electrolyte fuel cells (PEFCs) are developed using carbon nanofibers acting as catalyst supports or electrode fillers. In-situ colloidal impregnation enables to prepare highly-dispersed Pt electrode catalysts of a few nm in diameter on carbon black and carbon nanofibers including nanotubes. The addition of carbon fibers, forming continuous networks for electronic transport and forming open pore channels for gas transport, improves I-V characteristics of PEFCs..
413. K. Sasaki, K. Watanabe, K. Shiosaki, K. Susuki, and Y. Teraoka, Multi-fuel Capability of Solid Oxide Fuel Cells, JOURNAL OF ELECTROCERAMICS, 10.1007/s10832-004-5174-z, 13, 1-3, 669-675, 13 (1-3): 669-675 2004, 2004.11.
414. K. Sasaki, K. Shinya, S. Tanaka, Y. Kawazoe, T. Kuroki, K. Takata, H. Kusaba, and Y. Teraoka, Nanostructured PEFC Electrode Catalysts Prepared via In-situ Colloidal Impregnation, Mater. Res. Soc. Symp. Proc., 835, 241-246, Vol. 835, 241-46 (2004)., 2004.11.
415. K. Sasaki, K. Watanabe, and Y. Teraoka, Direct-alcohol SOFCs: Current-voltage characteristics and fuel gas compositions, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 10.1149/1.1756884, 151, 7, A965-A970, 151 (7): A965-A970 2004, 2004.07.
416. Yudi Pramono, Kazunari Sasaki, Toyohiko Yano, Release and diffusion rate of helium in neutron-irradiated SiC, journal of nuclear science and technology, 10.1080/18811248.2004.9715542, 41, 7, 751-755, 2004.07, [URL], Helium release measurements and diffusion coefficient calculations of helium in a neutron-irradiated α-SiC have been carried out in the temperature range of 750 1,260°C. The powder was obtained from SiC ceramics containing B4C, of which 10B concentration was 4.2×1016atom/mg. Neutron irradiation was conducted up to a fluence of 2.8×1024n/m2 (E>0.1 MeV) -300°C. The diffusion coefficients were calculated for the temperature region of 750-1,060°C with time range of 0-10 min. The diffusion coefficient of helium for SiC containing B4C was D (cm2/s)=1.38×1010exp[—0.91±0.07 (eV/atom)/kT]. Dissociative and interstitial diffusion mechanisms were supposed. Diffusion coefficients were reduced above -1,160°C probably due to accelerated migration of vacancies..
417. Ryuji Kikuchi, Yoshiaki Tanaka, Kazunari Sasaki, Koichi Eguchi, High temperature catalytic combustion of methane and propane over hexaaluminate catalysts
NOx emission characteristics, Catalysis Today, 10.1016/S0920-5861(03)00242-6, 83, 1-4, 223-231, 2003.08, [URL], Several hexaaluminate-related materials were prepared via hydrolysis of alkoxide and powder mixing method for high temperature combustion of CH4 and C3H8, in order to investigate the effect of the concentration of the fuels, O2 and H2O on NOx emission and combustion characteristics. Among the hexaaluminate catalysts, Sr0.8La0.2MnAl11O19-α prepared by the alkoxide method exhibited the highest activity for methane combustion and low NOx emission capability. NOx emission at 1500°C was increased linearly with O2 concentration, whereas water vapor addition decreased NOx emission in CH4 combustion over the Sr0.8La0.2MnAl11O19-α catalyst. In the catalytic combustion of C3H8 over the Sr0.8La0.2MnAl11O19-α catalyst, the amount of NOx emitted was raised in the temperature range between 1000 and 1500°C when the C3H8 concentration increased from 1 to 2 vol.%. It was found that NOx emission in this temperature range was reduced effectively by adding water vapor..
418. K. Sasaki and Y. Teraoka, Equilibria in fuel cell gases - II. The C-H-O ternary diagrams, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 10.1149/1.1577338, 150, 7, A885-A888, 150 (7): A885-A888 JUL 2003, 2003.07.
419. K. Sasaki and Y. Teraoka, Equilibria in fuel cell gases - I. Equilibrium compositions and reforming conditions, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 10.1149/1.1577337, 150, 7, A878-A884, 150 (7): A878-A884 JUL 2003, 2003.07.
420. Kazunari Sasaki, J. Maier, Chemical surface exchange of oxygen on Y2O 3-stabilized ZrO2, Solid State Ionics, 10.1016/S0167-2738(03)00264-9, 161, 1-2, 145-154, 2003.07, [URL], The chemical surface exchange of oxygen at single-crystalline Y 2O3-stabilized ZrO2 surfaces is studied using the in situ optical absorption relaxation technique. The surface exchange coefficients depend on temperature, oxygen partial pressure, and redox-active dopant concentration in a dilute concentration range; they depend only slightly on surface orientation, and become independent of annealing time after a long time treatment (typically at 800 °C). Using the thermodynamic factor of oxygen (which sensitively depends on redox-active impurities) derived from the known defect chemical parameters of this material, the effective macroscopic chemical rate constants are analyzed. The correlation with effective tracer rate coefficients is discussed for this model electron-poor ionic conductor..
421. Yohei Tanaka, Toshimasa Utaka, Ryuji Kikuchi, Tatsuya Takeguchi, Kazunari Sasaki, Koichi Eguchi, Water gas shift reaction for the reformed fuels over Cu/MnO catalysts prepared via spinel-type oxide, Journal of Catalysis, 10.1016/S0021-9517(03)00024-1, 215, 2, 271-278, 2003.04, [URL], Cu/MnO catalysts prepared via reduction of Cu-Mn spinel oxide were investigated for development of active Cu catalysts for the water gas shift reaction (WGSR). A Cu-Mn catalyst active for the WGSR was obtained after high temperature calcination at 900°C and subsequent reduction. The optimum Cu/ Mn ratio for catalytic activity of the Cu-Mn oxide system was 1/2. Nonstoichiometric Cu1.5Mn1.5O4 phase existed stably when copper manganese oxide was calcined above 700°C. The optimized Cu-Mn spinel showed excellent WGSR activity when a larger percentage of CO was used, as in hydrocarbon reforming. Cu-Mn spinel oxides calcined above 900°C were easily reduced. This may be responsible for the high activity of the Cu/ MnO catalyst. Carbon dioxide in the reformed gas significantly depressed WGSR activity below 200°C, while CO conversion reached equilibrium at 200°C in the absence of CO2..
422. Yohei Tanaka, Toshimasa Utaka, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, Water gas shift reaction over Cu-based mixed oxides for CO removal from the reformed fuels, Applied Catalysis A: General, 10.1016/S0926-860X(02)00529-X, 242, 2, 287-295, 2003.03, [URL], Cu-based mixed oxides were investigated for WGSR in order to identify catalysts with high activity and durability even under severe conditions including a large amount of H2O in the reformed fuels. CuAl2O4 and CuMn2O4 showed much higher specific rates of CO conversion than Cu/ZnO/Al2O3. Although WGSR activity emerged from reduction of the mixed oxides, high-temperature reduction gave rise to the sintering of Cu. CuAl2O4 showed moderate CO oxidation activity at lower temperatures and WGSR activity over 300 °C. The CuMn2O4 catalyst exhibited high WGSR activity over 225 °C, comparable to that of Cu/ZnO/Al2O3, and high durability for 20h at 200-225 °C..
423. S. Ayabe, H. Omoto, T. Utaka, R. Kikuchi, Kazunari Sasaki, Y. Teraoka, K. Eguchi, Catalytic autothermal reforming of methane and propane over supported metal catalysts, Applied Catalysis A: General, 10.1016/S0926-860X(02)00471-4, 241, 1-2, 261-269, 2003.02, [URL], Catalytic autothermal reforming of methane and propane over supported metal catalysts has been investigated in the present study. The carbon deposition region and the heat balance of the reaction have been determined from the equilibrium calculations. The sequence of the activities of the 2wt.% metal on alumina support for autothermal reforming of methane was Rh>Pd>Ni>Pt>Co. The catalytic activity of 10wt.% Ni/Al2O3 was higher than that of the 2wt.% Rh/Al2O3. The activity of Ni was significantly lowered by the preferential oxidation of the catalyst in the reactant gas at low temperatures. Although little carbon deposition was observed for the autothermal reforming of methane in the deposition-free region expected from the equilibrium, a large amount of carbon deposition was observed for the propane autothermal reforming even in the steam-rich conditions. The deposited carbon possessed fibrous morphology. The catalytic autothermal reforming appears to be initiated by decomposition of hydrocarbon at the inlet zone; then the reforming reaction subsequently proceeded in the catalyst bed..
424. Yohei Tanaka, Toshimasa Utaka, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, CO removal from reformed fuel over Cu/ZnO/Al2O3 catalysts prepared by impregnation and coprecipitation methods, Applied Catalysis A: General, 10.1016/S0926-860X(02)00095-9, 238, 1, 11-18, 2003.01, [URL], A composition of Cu/ZnO/Al2O3 catalysts prepared by the impregnation method was optimized for water gas shift reaction (WGSR) coupled with CO oxidation in the reformed gas. The optimum composition of the impregnated catalyst for high WGSR activity was 5wt.% Cu/5wt.% ZnO/Al 2O3. The optimum loading amounts of Cu and ZnO in the impregnated catalyst were smaller than those in the coprecipitated catalyst. Its catalytic activity above 200°C was comparable to that of the conventional coprecipitated Cu/ZnO/Al2O3 catalyst. However, the activity of the impregnated Cu/ZnO/Al2O3 catalysts was significantly lowered at 150°C, whereas no deactivation was observed for the coprecipitated catalyst at the same temperature. It was found that deactivation occurred over impregnated catalysts with H2O and/ or O2 in the reaction gas; it prevented CO adsorption on the surface..
425. Ryuji Kikuchi, Shingo Maeda, Kazunari Sasaki, Stefan Wennerström, Yasushi Ozawa, Koichi Eguchi, Catalytic activity of oxide-supported Pd catalysts on a honeycomb for low-temperature methane oxidation, Applied Catalysis A: General, 10.1016/S0926-860X(02)00387-3, 239, 1-2, 169-179, 2003.01, [URL], Low-temperature methane oxidation over oxide-supported Pd catalysts coated on a metal or ceramic honeycomb was investigated for gas turbine applications. Al2O3 and SnO2 were used as washcoat material, and a Fe-Cr-Al alloy and cordierite were adopted as metal and ceramic honeycombs, respectively. Pd catalysts on the honeycomb were prepared by varying washcoat loading and washcoat calcination temperature. It was found that the catalytic activities of Pd/SnO2 on metal and ceramic honeycombs improved with increasing washcoat loading and precalcination temperature of the washcoat material. Especially, significant enhancement of the catalytic activity appeared for Pd/SnO2/ceramic honeycomb as the washcoat loading increased from 150 to 200g/l. The catalytic activity of the honeycomb catalysts was examined under high pressure and space velocity. The temperature at which the increase in CH4 conversion became noticeable was shifted to higher temperature compared to the experiments at lower space velocity and ambient pressure. CH4 conversion over the honeycomb catalysts fluctuated as the catalyst bed inlet temperature was raised. Pd/SnO2/ceramic honeycomb exhibited the highest stable activity for low-temperature methane oxidation..
426. Suzue Kikuyama, Izumi Matsukuma, Tatsuya Takeguchi, Ryuji Kikuchi, Koichi Eguchi, Kazunari Sasaki, Nox sorption-desorption mechanism of ZrO2-based oxide, Studies in Surface Science and Catalysis, 145, 247-250, 2003.01, NOx sorption-desorption by zirconia-based sorbent, Pt-ZrO2/Al2O3 has been investigated. Oxidation of NO to NO2 and to nitrate ions is an important role for Pt. At low temperatures below 200°C, the oxidation activity of Pt is insufficient. As the sorption temperature increased, the amount of NOx desorbing at higher temperatures increased in comparison with the low temperature desorption in TPD. The chemical state of stored NOx species should be changed by reaction temperatures..
427. K. Eguchi, H. Kojo, T. Takeguchi, R. Kikuchi, K. Sasaki, Fuel flexibility in power generation by solid oxide fuel cells, Solid State Ionics, 10.1016/S0167-2738(02)00351-X, 152-153, 411-416, 2002.12, [URL], Power generation characteristics of solid oxide fuel cell (SOFC) with internal steam reforming of hydrocarbons were investigated. Steam reforming reaction over a Ni-YSZ cermet catalyst attained almost the equilibrium conversion and selectivity in the fixed bed reactor at 1000 °C. The conversion of internal reforming of hydrocarbons was incomplete because of the limited contact time with a thick layer of the Ni cermet electrode. Therefore, the fuel cell supplied with pre-reforming gas to the anode always gave rise to a lower terminal voltage because of the insufficient conversion of fuel compared with that supplied with post-reforming gas at a given current density. Methane internal reforming proceeded without deterioration with time, whereas the power generation with ethane and ethylene suffered from carbon deposition even at high steam-to-carbon ratio. Carbon deposition region and equilibrium partial pressure of oxygen in the C-H-O diagram were estimated from the thermodynamic data. The effect of the gas composition in the power generation characteristics, especially, difference in reactivity between H2 and CO, was investigated. The H2-H2O and CO-CO2 fuel systems led to almost the same open circuit voltage at the same H2/H2O and CO/CO2 ratios at 1000 °C, as expected from the thermodynamic equilibrium. The output voltage in a discharge condition was always higher for H2-H2O than for CO-CO2 at every current density..
428. Toyohisa Hoshikawa, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, Impedance analysis of electronic transport in dye-sensitized solar cells, Electrochemistry, 70, 9, 675-680, 2002.09, The ac impedance spectroscopy was applied to dye-sensitized solar cells with TiO2 or Nb2O5 as the semiconductor electrode. It was found that the impedance spectra consisted of three or four semicircles in the Nyquist representation. The arc with a characteristic frequency of a few hundred Hz was attributable to the electron transport between the semiconductor particles or within the particles, the arc at a few Hz to the electron transport at the electrode/dye/ electrolyte interface, and the arc at the frequency in the order of 10-1 Hz to the reduction of the electrolyte at the Pt electrode/electrolyte interface. The resistance of the arc at a few Hz decreased as the amount of the dye adsorbed on the TiO2 electrode and the irradiation intensity increased. When the Nb2O5 particles with large BET surface area were used as the electrode, the internal resistance of the solar cell was lowered; especially the shrinkage of the arcs in diameter at a few hundred Hz and a few Hz was significant..
429. Izumi Matsukuma, Suzue Kikuyama, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, Development of zirconia-based oxide sorbents for removal of NO and NO2, Applied Catalysis B: Environmental, 10.1016/S0926-3373(01)00329-0, 37, 2, 107-115, 2002.06, [URL], Zirconia-based oxide sorbents for NOx has been investigated to clarify the role of additives. Addition of yttria to Mn-Zr oxide improved the sorption capacity due to enhanced basicity and larger surface area. A Small amount of transition metal oxide as additives was effective in promoting the sorption-desorption capability. A small addition of Mn or Co to ZrO2 was effective in achieving reversible sorption and desorption of NOx due to their activity as a reduction-oxidation catalyst. These oxides were active for the oxidation of NO to nitrate ions via NO2 in an oxidizing atmosphere and reduction of nitrate ions in the presence of a gaseous reductant. The NOx sorptive capacities of Mn-containing sorbents were significantly deteriorated in dilute SO2. The NOx sorption capacity of 0.5 wt.% Co/ZrO2 was lowered only slightly in the initial stage of NO2 sorption with dilute SO2..
430. Ryuji Kikuchi, Shingo Maeda, Kazunari Sasaki, Stefan Wennerström, Koichi Eguchi, Low-temperature methane oxidation over oxide-supported Pd catalysts
Inhibitory effect of water vapor, Applied Catalysis A: General, 10.1016/S0926-860X(02)00096-0, 232, 1-2, 23-28, 2002.06, [URL], The influence of water vapor on the activity for low-temperature methane oxidation over oxide-supported catalysts such as Pd/Al2O3, Pd/SnO2, and Pd/Al2O3-36NiO was studied. It was found that Pd/Al2O3 was deactivated most significantly due to water vapor, and that Pd/Al2O3-36NiO was most insensitive to water vapor. The catalytic activity of Pd/Al2O3 decreased monotonically as water vapor concentration increased, whereas Pd/SnO2 and Pd/Al2O3-36NiO showed almost constant activity under higher water vapor concentrations. The catalytic activity at high steam concentration was in the following order: Pd/SnO2 > Pd/Al2O3-36NiO > Pd/Al2O3. Kinetic analysis with methane adsorption as the rate-limiting step was applied to evaluate the water inhibiting effect. Pd/Al2O3 displayed the most negative value of the enthalpy of water adsorption, while Pd/SnO2 and Pd/Al2O3-36NiO exhibited similar water adsorption enthalpy. Deactivation and regeneration of Pd/SnO2 and Pd/Al2O3 catalysts were investigated by cyclic feed of water vapor. Both the catalysts were deactivated rapidly upon switching on water feed, and then they regenerated gradually to the initial activity after the water feed was switched off..
431. Suzue Kikuyama, Izumi Matsukuma, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, A role of components in Pt-ZrO2/Al2O3 as a sorbent for removal of NO and NO2, Applied Catalysis A: General, 10.1016/S0926-860X(01)00879-1, 226, 1-2, 23-30, 2002.03, [URL], Oxide sorbents for NOx based on Pt-ZrO2/Al2O3 have been investigated. To clarify the role of each component, the sorption of NO and NO2 was compared using the samples composed of one or two components among Pt, ZrO2, and Al2O3. The sorption of NO and NO2 proceeded also on ZrO2, Al2O3, and ZrO2/Al2O3 without a Pt catalyst, but the rate of NOx removal was too slow to use any of them as sorbents. The NO2 removal was always higher than the NO removal on these oxides. These results indicate that the promotion of catalytic oxidation of NO to NO2 and successively to nitrate ions is an important role for the Pt catalyst. Although both alumina and zirconia demonstrated the NOx storage action, combination of the two components gave rise to the maximum capacity. The ZrO2 surface was more effective than the Al2O3 surface when NOx uptakes were compared per surface area basis. The FT-IR spectra after sorption of NO and NO2 demonstrated a strong band attributed to stored nitrate ions..
432. K. Sasaki, Y. Hori, R. Kikuchi, K. Eguchi, A. Ueno, H. Takeuchi, M. Aizawa, K. Tsujimoto, H. Tajiri, H. Nishikawa, Y. Uchidad, Current-voltage characteristics and impedance analysis of solid oxide fuel cells for mixed H2 and CO gases, Journal of the Electrochemical Society, 10.1149/1.1435357, 149, 3, A227-A233, 2002.03, [URL], Current-voltage (I-V) characteristics and electrode impedance of a tubular-type solid oxide fuel cell (SOFC) were analyzed for mixed fuel gases, consisting mainly of CO, H2, H2O, and a carrier gas, as simulated reformed gas of hydrocarbons or coal gas. I-V characteristics of a single cell were measured as a function of various operational parameters including the H2-to-CO ratio, the type of carrier gas such as He, N2, and Ar, the temperature, the fuel-to-carrier gas ratio, and the water vapor concentration. It has been experimentally confirmed that the use of CO-rich gases results in comparable performance to that of H2-rich gases and thus mixed gas such as coal gas is useful as a SOFC fuel. We have found, for the first time, that the I-V characteristics depend on the carrier gas, indicating the importance of gas transport in porous anodes for anodic polarization. The change in cell voltage by varying fuel compositions was mainly caused by the change in anode impedance associated with a low frequency semicircle in a Cole-Cole impedance plot at 1000°C. The fuel gas compositions in thermodynamic equilibrium were calculated and compared with the initial gas compositions, suggesting the importance of water vapor concentration to control the equilibrium H2-to-CO ratio for CO-rich fuel gases..
433. Kazunari Sasaki, Hideaki Kojo, Yuuichi Hori, Ryuji Kikuchi, Koichi Eguchi, Direct-alcohol/hydrocarbon SOFCs
Comparison of power generation characteristics for various fuels, Electrochemistry, 70, 1, 18-22, 2002.01, Various kinds of fuels based on alcohols (methanol, ethanol, and isopropanol) and hydrocarbons (methane, ethane, and ethylene) were directly supplied to solid oxide fuel cells (SOFCs) to compare their power generation characteristics. The results on current-voltage characteristics and anodic polarization have revealed that methanol-, ethanol-, and methane-based fuels exhibited satisfactory electrochemical performance, whereas the use of other carbonaceous fuels with a higher carbon number resulted in carbon deposition and consequent degradation of power generation characteristics. Importance of decomposition and/or reforming reactions of fuel species at the electrodes is highlighted..
434. Suzue Kikuyama, Izumi Matsukuma, Ryuji Kikuchi, Kazunari Sasaki, Koichi Eguchi, Effect of preparation methods on NOx removal ability by sorption in Pt-ZrO2-Al2O3, Applied Catalysis A: General, 10.1016/S0926-860X(01)00672-X, 219, 1-2, 107-116, 2001.10, [URL], Heterogeneous porous materials of Pt-ZrO2-Al2O3 are prepared via three different procedures based on impregnation and/or ammonia precipitation to examine their ability for NOx removal by sorption. In case a sample was prepared via ammonia precipitation, the sample exhibited both a larger BET surface area and a higher NO removal ability than a sample prepared only via impregnation. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt-ZrO2-Al2O3 prepared from H2PtCl6 in order to provide more active NOx sorption sites. This suggestion was supported by the experimental results: (1) the sample prepared using H2PtCl6 as a Pt source should be calcined at a higher temperature after the Pt source was added in order to exhibit a higher sorption ability, and (2) the use of Cl-free Pt sources enhanced the NOx sorptio n capacity even after calcination at a lower temperature..
435. Ryuji Kikuchi, Kazuhiko Takeda, Koshi Sekizawa, Kazunari Sasaki, Koichi Eguchi, Thick-film coating of hexaaluminate catalyst on ceramic substrates and its catalytic activity for high-temperature methane combustion, Applied Catalysis A: General, 10.1016/S0926-860X(01)00623-8, 218, 1-2, 101-111, 2001.09, [URL], Thick-film coating of hexaaluminate catalyst on thermally stable ceramic substrates and the catalytic activity of the film for methane oxidation were investigated for high-temperature combustion applications. The hexaaluminate film coated on pure alumina substrate retained the initial composition after calcination at 1200°C and displayed slightly lower catalytic activity than bulk hexaaluminate catalyst calcined at the same temperature. At the calcination temperatures of 1400 and 1600°C, migration of the components of the film and substrate occurred and the catalytic activity decreased considerably. The hexaaluminate catalyst film heat-treated at 1600°C was almost inactive for methane oxidation, which is attributable to volatilization of Mn during the heat treatment. By direct coating of the hexaaluminate on aluminum titanate honeycomb followed by calcination at 1200°C, the film exfoliated and cracks appeared in the aluminum titanate honeycomb. With an alumina intermediate layer inserted between the film and honeycomb, the thermal stability of the hexaaluminate film on the substrate calcined at 1200°C was significantly improved and the catalytic activity of the film was comparable to that of bulk hexaaluminate catalyst..
436. S. Raz, K. Sasaki, J. Maier, I. Riess, Characterization of adsorbed water layers on Y2O3-doped ZrO2, Solid State Ionics, 10.1016/S0167-2738(01)00826-8, 143, 2, 181-204, 2001.06, [URL], Chemisorption and physisorption of water from a humid atmosphere, on the oxide Y2O3-doped ZrO2 (YSZ), were investigated by conductivity measurements and thermogravimetry (TG), in the temperature range 35-700°C. Ionic conduction is indicated to take place in a thin layer of water adsorbed on the oxide. That ionic conduction is most probably proton conduction. At T < 600°C, it can exceed the oxygen ion conduction within the YSZ bulk when the oxide is made of fine powder. The electrical conductivity measurements of YSZ fine powder in humid atmosphere are analyzed in terms of water coverage, defect formation and proton mobility in the water layers. Further analysis of the water coverage is done using TG measurements. The enthalpies of defect formation and migration are determined. Results of preliminary conduction measurements of Al2O3 fine powder in a humid atmosphere reveal considerable similarities to those of YSZ..
437. K. Sasaki, J. Maier, Re-analysis of defect equilibria and transport parameters in Y2O3-stabilized ZrO2 using EPR and optical relaxation, Solid State Ionics, 10.1016/S0167-2738(00)00766-9, 134, 3-4, 303-321, 2000.10, [URL], The defect chemistry and transport properties of single-crystalline 9.5 mol% Y2O3-stabilized ZrO2 selectively doped with 3d transition metal or rare earth ions, are analyzed. In-situ and ex-situ EPR (ESR) and optical absorption spectroscopy are applied to quantify the concentrations of the redox-active ions in specific valence states as a function of temperature and oxygen partial pressure, as well as to measure the chemical diffusion coefficients of oxygen. Relevant self-consistent defect equilibrium constants (oxygen incorporation, dopant ion ionization) and transport coefficients (mobilities of electrons, holes, and oxygen vacancies) are extracted. The analysis uses the significance of trapping effects for the thermodynamic factor of oxygen, and the fact that the activity coefficient of oxygen vacancies, even though non-trivial, does not depend on pO2 or minor redox-active impurities..
438. Kazunari Sasaki, J. Maier, In situ EPR studies of chemical diffusion in oxides, Physical Chemistry Chemical Physics, 10.1039/b002850i, 2, 13, 3055-3061, 2000.07, [URL], Electron paramagnetic resonance (EPR) was applied as an in situ technique at high temperatures up to 1000°C for defect chemical and transport studies of ionic and mixed conductors. Equilibrium absorption intensities were examined as a function of oxygen partial pressure temperature and doping content for the model materials Y2O3-stabilized ZrO2 and Fe-doped SrTiO3. By this novel use of EPR in the field of solid state ionics, chemical diffusion coefficients and surface exchange coefficients of oxygen can be measured without any probe electrodes under diffusion conditions. This study moreover confirmed the ability to depress substantially the chemical diffusivity by using deep dopants such as Mn or Fe..
439. W. Schnelle, A. Poddar, P. Murugaraj, E. Gmelin, R. K. Kremer, K. Sasaki, J. Maier, Effect of annealing conditions on the physical properties of Nd0.67Sr0.33MnO3-δ, Journal of Physics Condensed Matter, 10.1088/0953-8984/12/19/310, 12, 19, 4401-4416, 2000.05, [URL], A study of the influence of annealing in atmospheres with defined oxygen partial pressures (1.5×10-6 Pa≤PO(2)≤10+5 Pa) on the electrical resistivity ρ(T), magnetic susceptibility χ(T), and heat capacity cp(T) of ceramic samples of Nd0.67Sr0.33MnO3-δ is presented. ρ(T) at 1000 °C shows no appreciable change for 10+2 Pa≤PO(2)≤10+5 Pa. For samples annealed in air a sharp peak is found in cp(T) and in ρ(T) at the ferromagnetic transition (TC≈238 K). The insulator-metal transition is observed below TC as a broad peak in ρ(T). Annealing at lower PO(2) leads to an increase of ρ whereas TC decreases only by ≈2 K. Annealing at PO(2)≤6.3×10-2 Pa suppresses TC and results in spin canting and a vanishing of the peak in cp(T). The specific heat (2-300 K) for samples annealed in air and in Ar/5% H2 is determined and thermodynamic standard values are calculated. The problem of the separation of cp(T) into lattice, electronic, and Mn and Nd magnetic contributions is discussed. cp(T<20 K) is dominated by a Schottky-like anomaly from the Zeeman-split ground-state doublet of Nd3+. A large quasi-linear term is mimicked by a broadening of the Schottky-like anomaly and by magnetic contributions from Mn in oxygen-deficient samples. The results are discussed in the context of oxygen deficiency δ, carrier concentration, defect chemistry, and disorder..
440. Koichi Eguchi, Hideyuki Koga, Koshi Sekizawa, Kazunari Sasaki, Nb2O5-based composite electrodes for dye-sensitized solar cells, Journal of the Ceramic Society of Japan, 108, 12, 1067-1071, 2000.01, Various semiconducting oxides are examined as alternative electrode materials for dye-sensitized solar cells. It was confirmed that Nb2O5-based electrodes exhibit a higher open-circuit voltage and fill factor, compared to TiO2-based electrodes. It was also found that a mixing of oxides, with a higher flat-band potential level such as SrTiO3, Ta2O5, and ZrO2, with Nb2O5 led to a higher open-circuit voltage. By mixing Nb2O5 with TiO2 in different ratios, it was revealed that these oxides form no chemical reaction products after a low-temperature heat treatment and a highest power output of the cells with the composite electrodes was obtained at Nb2O5 : TiO2 = 8 : 2 in mass. The power output with this composite electrode was higher than that with pure Nb2O5 or with pure TiO2. The Nb2O5-TiO2 composite electrode, in which the Nb2O5 particles are dispersed on the TiO2 surfaces, exhibits high photoelectrochemical performance..
441. Kazunari Sasaki, L. J. Gauckler, A model solid electrolyte/electrode material
ZrO2-ln2O3, Key Engineering Materials, 169-170, 197-200, 1999.12, ABSTRACT We have developed materials from the system ZrCVItCb, with which an ionic conductor, a mixedconducting composite, and an electronic conductor can be tailored only by varying the ratio of ZrU2 and In2O3. Phase equilibria, phase transformation, ionic and electronic conductivities, defect chemistry, chemical compatibility, thick film processing, and electrochemical properties are investigated. It is demonstrated that a cell with a cathode/electrolyte structure using ZrOi-IniCb exhibits satisfactory electrochemical performance, and that a functionally gradient electrode/electrolyte structure can be constructed to improve electrochemical properties..
442. K. Sasaki and J. Maier, Low-temperature defect chemistry of oxides. II. Analytical relations, JOURNAL OF APPLIED PHYSICS, 10.1063/1.371542, 86, 10, 5434-5443, 86 (10): 5434-5443 NOV 15 1999, 1999.11.
443. K. Sasaki and J. Maier, Low-temperature defect chemistry of oxides. I. General aspects and numerical calculations, JOURNAL OF APPLIED PHYSICS, 10.1063/1.371541, 86, 10, 5422-5433, 86 (10): 5422-5433 NOV 15 1999, 1999.11.
444. K. Sasaki, J. Claus, J. Maier, Defect chemistry of oxides in partially frozen-in states
Case studies for ZrO2(Y2O3), SrZrO3(Y2O3), and SrTiO3, Proceedings of the 1997 11th International Conference on Solid State Ionics, SSI-97
Solid State Ionics
, 10.1016/S0167-2738(98)00528-1, 121, 1, 51-60, 1999.06, [URL], The low temperature defect chemistry is analyzed for ZrO2(Y2O3), SrZrO3(Y2O3), and SrTiO3. In this temperature regime, the oxygen incorporation is no longer in equilibrium but the internal ionization reaction of electrons (holes) with redox-active impurities is still reversible. The concentration of ions with a specific valence state is quantified by EPR for ZrO2(Y2O3), while the electrical conductivity is considered for SrZrO3(Y2O3) and SrTiO3. It is shown that the experimental low-temperature results can well be explained in this way. If the experiments are appropriately conducted, an additional degree of freedom is introduced, which is the freezing-in temperature. The technological and scientific relevance with respect to materials research is discussed..
445. K. Sasaki, J. Maier, Low temperature defect chemistry of oxides, Journal of the European Ceramic Society, 10.1016/S0955-2219(98)00318-5, 19, 6-7, 741-745, 1999.06, [URL], Defect chemistry at lower temperatures, e.g. room temperature, is systematically described, at which the oxygen exchange reaction is no longer reversible. Analytical relations, numerical results, case studies as well as technological and scientific relevance are highlighted. It is pointed out that the low temperature defect chemistry also offers a quantitative basis to manipulate charge carrier and defect concentrations and related physical properties of oxide electroceramics..
446. K. Sasaki, M. Haseidl, J. Maier, Defect chemistry and transport properties of solid electrolytes including the influence of redox-active impurity ions, Key Engineering Materials, 169, 193-196, 1999.01, Defect chemistry and transport properties of solid electrolytes are discussed, including the influence of redox-active ions as well as ionic and electronic charge carriers. The defect chemical relations both in complete equilibrium at elevated temperatures and in partially frozen-in state at lower temperatures are described. Transport properties are described with respect to partial conductivities, defect diffusion coefficients, and the chemical diffusion and surface exchange coefficients of oxygen. In-situ and ex-situ optical absorption and EPR are applied. A case study for single crystalline selectively impurity-doped ZrO2(Y2O3) as a model material is presented..
447. K. Sasaki, J. Maier, Low temperature defect chemistry of oxide electroceramics, Key Engineering Materials, 169, 189-192, 1999.01, Defect chemistry of oxides at lower temperatures, e.g. room temperature, especially for electronics applications is analyzed, at which the oxygen exchange equilibrium reaction is no longer reversible but the internal ionization equilibrium reactions, in particular electronic transfer processes, are still reversible. Defect concentrations at such a temperature can be derived numerically as well as analytically. It is pointed out that the low temperature defect chemistry offers a quantitative basis to manipulate charge carrier and defect concentrations and related physical properties of oxide electroceramics..
448. Kazunari Sasaki, L. J. Gauckler, Microstructure-property relations of SOFC electrodes
Importance of microstructural optimization of La(Sr)MnO3 cathodes on ZrO2(Y2O3) electrolytes, Key Engineering Materials, 169, 201-204, 1999, Microstructure, cathodic polarization, and ohmic losses of cathodes for SOFCs operating around 800 °C are studied. The importance of the electrode microstructure on electrochemical properties is demonstrated using the La0.85Sr0.15MnO3 cathode material on the ZrO2-8mol%Y2O3 electrolytes. It is revealed that the reduction of the current constriction is the key for optimizing electrochemical performance on microscopic level near the three phase boundaries as well as on macroscopic level around contacts with current collectors..
449. M. Gödickemeier, K. Sasaki, L. J. Gauckler, I. Riess, Electrochemical characteristics of cathodes in solid oxide fuel cells based on ceria electrolytes, Journal of the Electrochemical Society, 10.1149/1.1837653, 144, 5, 1635-1646, 1997.01, [URL], The ionic current-overpotential characteristics of cathodes on ceria-based electrolytes have been evaluated by galvanostatic current-interrupt measurements. The measurements were carried out on mixed conducting ceria electrolytes under fuel cell operating conditions. The effect on the oxygen reduction kinetics of the simultaneous transport of electrons and oxygen was investigated. As model substances for cathodes were La0.8Sr0.2MnO3, La0.84Sr0.16CoO3, Pt, Ag, and Au. Cathode reaction mechanisms as a function of the transport properties are discussed for the different cathode materials. Steady-state cathode overpotentials were interpreted using a Butler-Volmer-type equation to describe charge-transfer processes and to evaluate exchange current densities. At 700°C the exchange current density of the best cathode La0.84Sr0.16CoO3 was 180 mA/cm2 whereas the one for La0.8Sr0.2MnO3 was only 30 mA/cm2. In both cases we identified charge-transfer on the cathode material as the rate-limiting step..
450. Kazunari Sasaki, Ludwig J. Gauckler, Microstructure-property relations of solid oxide fuel cells. Microstructural design of cathodes and current collectors, Denki Kagaku, 64, 6, 654-661, 1996.12, Microstructure-property relations of solid oxide fuel cells are studied using ZrO2-In2O3 as a model electrolyte/electrode, and ZrO2(Y2O3)-La0 85Sr0.15MnO3-Pt mesh as a model electrolyte/electrode/current collector. Electrochemical performance of the cells depends strongly on the microstructure of electrode as well as the geometry of the current collectors. A decrease in effective electrode area occurs both on the microscopic level with a coarse and inhomogeneous electrode microstructure and on the microscopic level with a wide contact spacing of the current collectors. Microstructure tailoring as well as the current collector geometry becomes important with decreasing operation temperature of the fuel cells..
451. Kazunari Sasaki, Ludwig J. Gauckler, Microstructure-property relations of solid oxide fuel cells. Microstructural design of cathodes and current collectors, Electrochemistry, 64, 6, 654-661, 1996.12, Microstructure-property relations of solid oxide fuel cells are studied using ZrO2-In2O3 as a model electrolyte/electrode, and ZrO2(Y2O3)-La0.85Sr 0.15MnO3-Pt mesh as a model electrolyte/electrode/current collector. Electrochemical performance of the cells depends strongly on the microstructure of electrode as well as the geometry of the current collectors. A decrease in effective electrode area occurs both on the microscopic level with a coarse and inhomogeneous electrode microstructure and on the microscopic level with a wide contact spacing of the current collectors. Microstructure tailoring as well as the current collector geometry becomes important with decreasing operation temperalure of the fuel cells..
452. M. Gödickemeier, K. Sasaki, L. J. Gauckler, I. Riess, Perovskite cathodes for solid oxide fuel cells based on ceria electrolytes, Solid State Ionics, 10.1016/0167-2738(96)00149-X, 86-88, PART 2, 691-701, 1996.07, [URL], The ionic current-overpotential characteristics of cathodes on ceria-based electrolytes have been evaluated by galvanostatic current-interruption measurements under fuel cell operating conditions. The effect of either mixed ionic electronic conductivity or high oxygen diffusivity on the oxygen reduction kinetics was investigated. La0.8Sr0.2MnO3 served as a model substance for cathodes with a high activity for oxygen reduction and a low oxygen ionic conductivity. The behaviour of La0.8Sr0.2MnO3 is compared to that of La0.84Sr0.16CoO3 which shows high activity for oxygen reduction and high oxygen diffusivity..
453. K. Sasaki, J. P. Wurth, R. Gschwend, M. Gödickemeier, L. J. Gauckler, Microstructure-property relations of solid oxide fuel cell cathodes and current collectors cathodic polarization and ohmic resistance, Journal of the Electrochemical Society, 10.1149/1.1836476, 143, 2, 530-543, 1996.02, [URL], Microstructure, cathodic polarization, and ohmic resistance on the cathode side of ZrO2-based solid oxide fuel cells have been studied for the intermediate temperature operation range between 700 and 900°C. Starting powder characteristics, powder calcination temperature, and sintering temperature strongly influence the final microstructure of cathodes. Electrochemical performance depends on these processing parameters as well as on the cathode thickness and the contact spacing of current collectors. A decrease in effective electrode area occurs both on the microscopic level with coarse and inhomogeneous cathode microstructure and on the macroscopic level with a wide contact spacing of the current collectors. The smaller effective electrode area causes inhomogeneous current density distribution and results consequently in higher ohmic losses originating from the electrolyte and higher cathodic polarization. These losses are evaluated using La0.35Sr0.15MnO3 cathodes with different microstructures and on the ZrO2-8 mole percent Y2O3 electrolyte. The influence of current path constrictions on the ohmic and nonohmic losses is demonstrated using Pt current collectors of different geometric spacings..
454. L. J. Gauckler, K. Sasaki, Ionic and electronic conductivities of homogeneous and heterogeneous materials in the system ZrO2In2O3, Solid State Ionics, 10.1016/0167-2738(94)00145-I, 75, C, 203-210, 1995.01, [URL], In the system ZrO2In2O3, the In2O3-doped ZrO2 phases (cubic, tetragonal and t́) exhibit high ionic conductivity and the ZrO2-doped In2O3 high electronic conductivity. These phases are in thermodynamic equilibrium at high temperatures. The ionic conductivity of ZrO2 depends on the crystal symmetry having the same In2O3 concentration. At 1000 °C, the highest conductivities were obtained for cubic ZrO2 doped with 25 mol% InO1.5. At lower concentrations, the ionic conductivity of cubic-ZrO2 decreases due to a first-order phase transformation to the tetragonal (t́) form. Single-phase In2O3 doped with ZrO2 is an n-type electronic conductor with a conductivity of up to 7 × 104 S m in air. Point defect models for electronic conduction in In2O3 doped with ZrO2 are discussed. Two maxima in the electronic conductivity have been found: one in the two-phase region and one in the InO1.5 single phase region. In the heterogeneous two-phase material cubic-ZrO2 + InO1.5, the electronic conductivity increases abruptly up to 104 S m with increasing InO1.5 concentration. This material is a three-dimensional composite of ion- and electron-conducting phases. The origin of the maximum in electrical conductivity in the heterogeneous two-phase region is discussed..
455. A. Orliukas, P. Bohac, K. Sasaki, L. J. Gauckler, The relaxation dispersion of the ionic conductivity in cubic zirconias, Solid State Ionics, 10.1016/0167-2738(94)90121-X, 72, PART 2, 35-38, 1994.09, [URL], The relaxation dispersion of the bulk ionic conductivity of cubic zirconias stabilized with yttria, calcia and magnesia has been investigated between 450 and 1200 K at frequencies ranging from 20 Hz to 1.2 GHz. The relaxation process is attributed to the diffusional polarization due to the short-range oxygen vacancy jumping in the crystal lattice and allows one to determine the corresponding diffusion coefficients as well as the mobilities of oxygen vacancies. A good agreement was found between the activation energy of the ionic conductivity and the activation energy of the diffusion of charge carriers. The calculated concentration of mobile oxygen vacancies does not change with temperature and is equal to the concentration of all extrinsic oxygen vacancies created by doping..
456. M. Godickemeiei, B. Michel, A. Orliukas, P. Bohac, K. Sasaki, L. Gauckler, H. Heinrich, P. Schwander, G. Kostorz, H. Hofmann, O. Frei, Effect of intergranular glass films on the electrical conductivity of 3Y-TZP, Journal of Materials Research, 10.1557/JMR.1994.1228, 9, 5, 1228-1240, 1994.05, [URL], The electrical conductivity of 3Y-TZP ceramics containing Si02 and A1203 has been investigated by complex impedance spectroscopy between 500 and 1270 K. At low temperatures, the total electrical conductivity is suppressed by the grain boundary glass films. The equilibrium thickness of intergranular films is 1–2 nm, as derived using the “brick-layer” model and measured by HRTEM. A change in the slope of the conductivity Arrhenius plots occurs at the characteristic temperature Th at which the macroscopic grain boundary resistivity has the same value as the resistivity of the grains. The temperature dependence of the conductivity is discussed in terms of a series combination of RC elements..
457. K. Sasaki, H. P. Seifert, L. J. Gauckler, Electronic Conductivity of Ln2O3 Solid Solutions with ZrO2, Journal of the Electrochemical Society, 10.1149/1.2059204, 141, 10, 2759-2768, 1994.01, [URL], The electrical conductivity of In2O3-ZrO2 as well as ln2O3 solid solutions doped with SnO2, CeO2, Nb2O5, Pr6O11, and MgO is investigated, in the temperature range between room temperature and 1300°C, and in the oxygen partial pressure range between 5 X 10-5 and 1 atm. In2O3 doped with ZrO2 is an electronic conductor, while ZrO2 doped with ln2O3 is an oxygen-ionic conductor. The two-phase material of the cubic (fcc) ZrO2+ cubic (bcc) ln2O3 solid solutions is a 3-dimensional composite of ionic and electronic conductors. The single-phase ln2O3 doped with ZrO2 is an electronic conductor with a conductivity up to 7 X 104Sm-1 in air. Two maxima in electrical conductivity are found, one in the two-phase region and one in the ln2O3 single-phase region. Lattice defects responsible for electronic conduction in pure and doped ln2O3 are discussed. The defect models for ln2O3 doped with ZrO2 are proposed, and the Kroger-Vink diagram is constructed. The metastable solubility of dopants in ln2O3 due to the slow phase separation kinetics influences the electronic conductivity. ZrO2 is a most effective donor for increasing electronic conductivity of ln2O3, among hypervalent metal oxides including SnO2, Nb2O5; and CeO3..
458. Kazunari Sasaki, Petr Bohac, Ludwig J. Gauckler, Phase Equilibria in the System ZrO2─InO1.5, Journal of the American Ceramic Society, 10.1111/j.1151-2916.1993.tb03661.x, 76, 3, 689-698, 1993.01, [URL], Phase equilibria in the system ZrO2─InO1.5 have been investigated in the temperature range from 800° to 1700°C Up to 4 mol%, InO1.5 is soluble in t‐ZrO2 at 1500°C. The martensitic transformation temperature m→t of ZrO2 containing InO1.5 is compared with that of ZrO2 solid solutions with various other trivalent ions with different ionic radii. The diffusionless c→t′ A phase transformation is discussed. Extended solid solubility from 12.4 ± 0.8 to 56.5 ± 3 mol% InO1.5 is found at 1700°C in the cubic ZrO2 phase. The eutectoid composition and temperature for the decomposition of c‐ZrO2 solid solution into t‐ZrO2+InO1.5 solid solutions were determined. A maximum of about 1 mol% ZrO2 is soluble in bcc InO1.5 phase. Metastable supersaturation of ZrO2 in bcc InO 1.5 and conditions for phase separation are discussed..
459. A. Orliukas, P. Bohac, Kazunari Sasaki, L. Gauckler, Relaxation dispersion of ionic conductivity in a Zr0·85Ca0·15O1·85 single crystal, Journal of the European Ceramic Society, 10.1016/0955-2219(93)90127-D, 12, 2, 87-96, 1993.01, [URL], The dynamic behavior of the oxygen ion conductivity of a cubic Zr0·85Ca0·15O1·85 single crystal has been investigated with AC impedance spectroscopy and a dynamic pulse method as a function of both temperature and frequency between 450 and 1200 K and 20 and 108 Hz. This is the frequency-temperature range where the relaxation dispersion of the ionic conductivity can be observed. From the temperature dependence of the relaxation frequency, the diffusion coefficient and the mobility of oxygen vacancies were determined. In the entire temperature range investigated, the temperature dependence of the ionic conductivity of a Zr0·85Ca0·15O1·85 single crystal arises exclusively from the temperature dependence of the mobility of oxygen vacancies, the concentration of which remains constant with temperature and is equal to the concentration of all extrinsic oxygen vacancies created by calcia stabilizing. No transition in the Arrhenius plot of the ionic conductivity due to a gradual dissociation of oxygen vacancy-defect cation associates, as proposed in the literature, has been observed. A simple model for the temperature dependence of the ionic conductivity of solid electrolytes in terms of the parallel and serial combination of RC-elements is given..
460. K. Sasaki, T. Yano, T. Maruyama, T. Iseki, Helium release and microstructure of neutron-irradiated SiC ceramics, Journal of Nuclear Materials, 10.1016/0022-3115(91)90111-J, 179-181, PART 1, 407-410, 1991.01, [URL], α-SiC ceramics containing 10B were neutron-irradiated in the JMTR to a fluence of 6.0 × 1024 n/m2 (E > 1 MeV) at 650° C. Helium release from SiC ceramics and powders was measured up to 2000° C. Microstructural observation by TEM was also carried out on SiC specimens annealed at temperatures in the range 1200-2000 °C. The helium release rate of the powder specimen started to increase at about 800°C and two peaks were observed at 1100 and 1260°C. By contrast, the sintered specimen showed a low gas release rate up to 1800°C and exhibited a rapid increase above this temperature. The helium release mechanism from the sintered specimen was discussed in terms of the mobility of helium atoms and vacancies, and bubbles at grain boundaries..
461. Toyohiko Yano, Kazunari Sasaki, Tadashi Maruyama, Takayoshi Iseki, Masahiko Ito, Shoji Onose, Step-heating dilatometry method to measure the change in length due to annealing of a SiC temperature monitor, Nuclear Technology, 10.13182/NT91-A34535, 93, 3, 412-415, 1991.01, [URL], A simple method to measure the change in length of a silicon carbide temperature monitor due to annealing is presented. A differential dilatometer is used to detect the change in length of an irradiated specimen as the temperature of the specimen is raised in steps. The results obtained by this step-heating dilatometry method are in good agreement with measurements obtained with an X-ray diffractometer and a micrometer..
462. K. Sasaki, T. Maruyama, T. Iseki, Helium release from neutron-irradiated SiC containing 10B isotope, Journal of Nuclear Materials, 10.1016/0022-3115(89)90604-1, 168, 3, 349-351, 1989.12, [URL].
463. Kazunari Sasaki, Kenji Shinya, Shuhei Tanaka, Atsushi Furukawa, Kentaro Ando, Takashi Kuroki, Hajime Kusaba, Yasutake Teraoka, Nanostructuring of PEFC Electrode Catalysts Using Carbon Nanofibers, Proceedings 4th International Symposium Proton Conducting Membrane Fuel Cells, Vol. 2004-21, pp.159-170.

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