| 1. |
Yuya Tachikawa, Yoshio Matsuzaki, Yasuharu Kawabata, Shunsuke Taniguchi, Kazunari Sasaki, Numerical Study on Biogas Refining System Combined with Proton-Conducting Solid Oxide Electrolyzer, The 17th International Symposium on Solid Oxide Fuel Cells (SOFC-XVII), 2021.07. |
| 2. |
TACHIKAWA Yuya, MATSUZAKI Yoshio, KAWABATA Yasuharu, SATO Koki, IINUMA Hiroki, BABA Yoshitaka, FUKUNAGA Eiichi, TANIGUCHI Shunsuke, SASAKI Kazunari
, Process Analysis of Biogas Refining System using Proton Conducting SOEC, The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), 2019.10. |
| 3. |
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, 2019.01, 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.. |
| 4. |
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, 2019.01, 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.. |
| 5. |
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, 2019.01, 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.. |
| 6. |
Aki MURAMOTO, Yudai KiKUCHI, Yuya TACHIKAWA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, C-H-O Diagrams for Solid Oxide Fuel Cells, AiMES2018, 2018.10. |
| 7. |
Keisuke TAKINO, Yuya TACHIKAWA, Yusuke SHIRATORI, Shunsuke TANIGUCHI, Kazunari SASAKI, Simulation and Visualization of Cell Performance Distribution of SOFCs, AiMES2018, 2018.10. |
| 8. |
Yusuke ISHIBASHI, Shotaro FUTAMURA, Yuya TACHIKAWA, Junko MATSUDA, Yusuke SHIRATORI, ShunsukeTANIGUCHI, Kazunari SASAKI, Preparation and Characterization of Alternative Ni-Based Anode Materials for SOFCs, AiMES2018, 2018.10. |
| 9. |
Yuya TACHIKAWA, Yoshio MATSUZAKI, Yoshitaka BABA, Hiroki IINUMA, Koki SATO, Shunsuke TANIGUCHI, Kazunari SASAKI, Development of Solid Oxide Fuel Cell System Concept for Low Carbon Emission, 12th International Conference for Ceramic Materials and Components for Energy and Environmental Applications, 2018.07. |
| 10. |
Yuya TACHIKAWA, Yoshio MATSUZAKI, Takaaki SOMEKAWA, Koki SATO, Shunsuke TANIGUCHI, Kazunari SASAKI, Solid Oxide Electrolyzer Devices using Proton and Oxide-ion Conducting Electrolyte, 13th EUROPEAN SOFC & SOE FORUM 2018, 2018.07. |
| 11. |
Yoshio MATSUZAKI, Yuya TACHIKAWA, Koki SATO, Takaaki SOMEKAWA, Junichiro OTOMO, Hiroshige MATSUMOTO, Shunsuke TANIGUCHI, Kazunari SASAKI, Modified Energy Efficiencies of Proton-conducting SOFCs with Partial Conductions of Oxide-ions and Holes, 13th EUROPEAN SOFC & SOE FORUM 2018, 2018.07. |
| 12. |
S. Futamura, Yuya Tachikawa, Junko Matsuda, Stephen Matthew Lyth, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari Sasaki, Alternative SOFC anode materials with ion- and electron-conducting backbones for higher fuel utilization, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Redox-stable anodes are developed for zirconia-based electrolyte-supported solid oxide fuel cells (SOFCs) operating at high fuel utilization, as an alternative to the Ni yttrium-stabilized-zirconia (YSZ) cermet. Gadolinium-doped ceria (GDC, Ce0.9Gd0.1O2) is utilized as a mixed ionic electronic conductor (MIEC), and combined with lanthanum-doped strontium titanate (LST, Sr0.9La0.1TiO3) as an electronic conductor. Catalyst nanoparticles (either Ni or Rh) are incorporated via impregnation. The electrochemical characteristics of SOFC single cells using these anodes are characterized in humidified H2 at 800°C. The stability against redox cycling and under high fuel utilization is analyzed and discussed.. |
| 13. |
Y. Kikuchi, Junko Matsuda, Yuya Tachikawa, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari Sasaki, Degradation of SOFCs by various impurities
Impedance spectroscopy and microstructural analysis, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, SOFC can use various kinds of fuels besides hydrogen, including city gas, coal gas, digestion gas, and biogas. On the other hand, it is known that such practical fuels contain various fuel impurities such as sulfur, phosphorus, and siloxane, affecting fuel cell performance and durability. Here, a case study for siloxane as a model SOFC fuel impurity is made to understand the impurity poisoning phenomena through both electrochemical and microstructural analysis to analyze poisoning processes, especially by applying the DRT (Distribution of Relaxation Times) analysis.. |
| 14. |
Yuya Tachikawa, Y. Matsuzaki, Y. Kawabata, M. Sugahara, T. Somekawa, Shunsuke Taniguchi, Kazunari Sasaki, Effect of carbon-neutral fuel fed solid oxide fuel cell system on CO2 emission reduction, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Carbon-neutral fuel fed solid oxide fuel cell (SOFC) system can achieve highly efficient power generation without any greenhouse gas emissions. In this paper, the influence of supplied fuel species on the SOFC performance has been evaluated by heat and mass balance analysis. The electrical efficiency of carbon-neutral fuel fed SOFCs is quantified and compared with that of conventional fuel supplied SOFCs. Then, the effect of electrical efficiency increase on CO2 emission is also quantified. Furthermore, the effect of proton-conducting ceramic materials application as an electrolyte is also discussed to evaluate the influence on electrical efficiency. The carbon-neutral fuel fed protonic ceramic fuel cells (PCFCs) had an advantage to enhance their electrical efficiencies compared with the same fuels fed typical SOFCs. Due to the increase in electrical efficiency, the CO2 emission reduction clearly appeared as CO2 emission factor.. |
| 15. |
K. Takino, Yuya Tachikawa, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari Sasaki, Effect of exchange current density on current distribution at planar-type SOFC anodes, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Cell stack structure of solid oxide fuel cells (SOFCs) affects their performance; its optimization is important to realize highly efficient SOFCs. In this study, we focus on the numerical simulation method combined with experimentally obtained exchange current density. Deriving the anode exchange current density for fully pre-reformed methane-fueled SOFCs, the effect on the current distribution is evaluated. Current distribution was calculated using variable anode exchange current density after taking into account the pressures of CO and CO2.. |
| 16. |
A. Muramoto, Y. Kikuchi, Yuya Tachikawa, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari Sasaki, Fuel composition in pressurized SOFCs, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Pressurized SOFCs operate at high temperatures and generate electricity by using various fuel species. SOFCs can be applied for large-scale power generation combined with gas and steam turbine(s) under high pressure. In this study, fuel gas composition is systematically considered by thermochemical calculations on the anode side of the SOFCs pressurized up to 30 bar in a wide temperature range up to 1000oC. In general, fuel gas consists mainly of carbon, hydrogen, and oxygen, so that the C-H-O equilibrium diagrams have been calculated for different cases. It is revealed that carbon deposition region contracts in the hydrogenrich area and expands in the oxygen-rich area with increasing the total pressure. The molar fraction of each gas component also depends also on the total pressure.. |
| 17. |
Y. Wakita, Yuya Tachikawa, Hironori Nakajima, Kohei Ito, Glass shape change during firing for improving the seal of planar SOFCs, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Secure sealing is vital for planar type SOFCs to avoid the performance degradation and achieve long-term stable operation. Here we focus on the sheet type glass sealing which is produced by tape-casting method. High wettability of the glass is essential to avoid the stress concentration because low wettability increases the contact angle of the glass and makes the notch at the edge of glass sealing interface. We have evaluated the effect of temperature rising rate on the wettability of the sealing glass and the edge shape of it using the visualization test system. High temperature rising rate led to small contact angle of the sealing glass in some cases and can mitigate the stress concentration.. |
| 18. |
Y. Kawabata, Yuya Tachikawa, Shunsuke Taniguchi, Y. Matsuzaki, Kazunari Sasaki, New applications of SOFC-MGT hybrid power generation system for low-carbon society, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, Solid oxide fuel cell (SOFC) is one of the efficient power generation technologies which have high applicability to use various kinds of fuels including city gas, coal, and biomass. As SOFC can transport oxygen ions from the cathode side to the anode side, the exhaust anode off-gas contains CO2 and H2O only, so that CO2 can be captured simply by cooling the exhaust gas. This means that we can, in principle, develop highly-efficient CO2-capture SOFC power generation system by integrating efficient oxygen production system and exhaust gas cooling system. In this paper, we propose CO2-capture SOFC-Micro Gas Turbine (MGT) hybrid power generation system as a new application towards low-carbon society. Results of feasibility study and performance analysis indicated great potential and high applicability of efficient CO2-capture power generation solutions.. |
| 19. |
Y. Matsuzaki, Yuya Tachikawa, T. Somekawa, K. Sato, Y. Kawabata, M. Sugahara, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari Sasaki, Relationship between electrochemical properties and electrolyte partial conductivities of proton-conducting ceramic fuel cells, 15th International Symposium on Solid Oxide Fuel Cells, SOFC 2017, 2017.05, The electrochemical properties of the proton-conducting ceramic fuel cells (PCFCs) with BaZr0.1Ce0.7Y0.1X0.1O3-δ (BZCYX, X = Ga, Sc, In, Yb, or Gd) electrolytes have been investigated. BZCYX materials were found to have various partial conductivities of charge-carriers such as ion, hole, and electron. The electrochemical properties exhibited strong dependences on operation conditions. When ASR and external current density were fixed at 0.4 Ω cm2 and 0.25 A cm-2, respectively, the electrical efficiency, η(X), was found to have the following sequential order: η(Sc) > η(In) > η(Ga) > η(Yb) > η(Gd). On the other hand, when ASR was not fixed but the thickness of the electrolyte was fixed at 25 μm, large variations appeared in the leakage current of the cells with the BZCYX electrolytes. The sequential order of the electrical efficiency with the fixed thickness was different from that with the fixed ASR as described in the above inequality expression, and depends on the operating temperature. The ratios of the leakage current with X = Yb or Gd were higher than those with X = Ga, Sc, or In. These high ratios were found to cause the serious drop in the electrical efficiency at an external current density of 0.25 A cm-2. We have successfully found out the candidates for the X element in BZCYX, by which high-efficient power generation would be expected.. |
| 20. |
H. Anai, Junko Matsuda, Z. Noda, Yuya Tachikawa, Akari Hayashi, Kohei Ito, Kazunari Sasaki, Preparation of iridium/SnO2/VGCF electrocatalysts for water electrolysis, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting, 2016, 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.. |
| 21. |
T. Kawasaki, J. Sugimoto, Yuya Tachikawa, Yusuke Shiratori, Shunsuke Taniguchi, Kazunari 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, 2015.01, 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.. |
| 22. |
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, 2015, 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.. |
| 23. |
Y. Matsuzaki, Yuya Tachikawa, T. Hatae, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari 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, 2015, 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.. |
| 24. |
Yuya Tachikawa, Y. Matsuzaki, T. Hatae, Shunsuke Taniguchi, Kazunari 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, 2015, 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.. |
| 25. |
Kazunari Sasaki, Shunsuke Taniguchi, Yusuke Shiratori, Akari Hayashi, T. Oshima, Masamichi Nishihara, Yuya 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, 2015, 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.. |
| 26. |
Yuya Tachikawa, T. Kawabata, Yusuke Shiratori, Kazunari 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, 2015, 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.. |
| 27. |
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, Symposium on Materials Degradation in Energy Systems: Corrosion and Hydrogen-Material Interactions - 22nd ECS Meeting/PRiME 2012, 2012, Chromium poisoning phenomena were compared among three SOFC cathodes consisting of Lai0.8Sr0.2MnO3 (LSM), Lai 0.06Sri0.4Fei0.8Co0.2O3 (LSCF) and LaNii0.06Fei0.4O3 (LNF) under relatively large cathode polarization conditions. Deposition of chromium near the cathode/electrolyte interface seems to be affected only by the cathode polarization, not by the cathode materials nor the current density.. |
| 28. |
T. Yonekura, Yuya Tachikawa, T. Yoshizumi, Yusuke Shiratori, Kohei Ito, Kazunari Sasaki, Exchange current density of solid oxide fuel cell electrodes, 12th International Symposium on Solid Oxide Fuel Cells, SOFC-XII - 219th ECS Meeting, 2011.12, 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.. |
