Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Kohei Ito Last modified date:2018.07.03

Professor / Hydrogen Utilization Engineering / Department of Mechanical Engineering / Faculty of Engineering


Papers
1. Hua Li, Hironori Nakajima, Akiko Inada, Kohei Ito, Effect of flow-field pattern and flow configuration on the performance of a polymer-electrolyte-membrane water electrolyzer at high temperature, International Journal of Hydrogen Energy, Vol.43, No.18, (2018), pp.8600-8610, 10.1016/j.ijhydene.2018.02.171, 2018.01, This study aimed to optimize the flow-field pattern and flow configuration of a polymer-electrolyte-membrane water electrolyzer, with a particular focus on high-temperature operation up to 120 °C. Three types of flow-field pattern (serpentine, parallel, and cascade) were tested in both the anode and cathode sides of a water electrolyzer cell, and the current-voltage characteristics and high-frequency resistance were measured to examine which overpotential components are impacted by the flow-field pattern. The experimental results revealed that the cathode flow-field pattern only affects the ohmic overpotential, while the anode flow-field pattern significantly affects the overpotential related to liquid water shortage at catalyst layer, and the flow configuration (counter- and co-flow) does not affect the electrolysis performance. Finally, under operating conditions of 120 °C and 0.3 MPa, we found that the optimized cell configuration consisted of cascade and serpentine flow-field patterns in the anode and cathode, respectively; this configuration produced the minimum electrolysis voltage of 1.69 V at 2 A/cm2..
2. K. Ito, K. Terabaru, H. Li, A. Inada, H. NAKAJIMA, Challenging of Reducing Electrolysis Voltage by Superimposing Boiling on PEMWE–A Thermodynamic Coupling–, ECS Trans. 2017 80(8): 1117-1125, doi:10.1149/08008.1117ecst, 80, 8, 2017.10, This study challenges to decrease water electrolysis voltage by thermodynamic coupling between boiling and water electrolysis. Boiling, once a system to cause boiling is given, spontaneously advances and causes entropy generation. When boiling is superimposed on an electrode where electrochemical reaction of water electrolysis progress, the entropy generation by the boiling possibly accelerates the reaction of water electrolysis, leading to reduction of electrolysis voltage. To confirm this new concept, electrolysis voltage for a unit cell of PEMWE is measured in the region from 80°C to 120°C under a condition that cell pressure and electrolysis current are kept constant. The measurement results showed that the electrolysis voltage abruptly decrease as cell temperature crosses boiling point and then turn to increase at a few degree higher than the point. These features in the measurement were reproduced in the theoretical analysis based on a mathematical model considering the thermodynamic coupling..
3. Y. Wakita, Y. Tachikawa, H. Nakajima, K. Ito, Glass shape change during firing for improving the seal of planar SOFCs, ECS Transactions 78 (1), pp.1731-1737 (2017), 78 (1), pp.1731-1737 (2017), 2017.06.
4. Tsuyohiko Fujigaya, Yilei Shi, Jun Yang, Hua Li,, Kohei Ito, Naotoshi Nakashima, A highly efficient and durable carbon nanotube-based anode electrocatalyst for water electrolyzers, J. Mater. Chem. A, 2017, 10.1039/c7ta01318c, 75, 14, 2017.05.
5. Hua Li, Tsuyohiko Fujigaya, Hironori NAKAJIMA, Akiko Inada, Kohei Ito, Optimum structural properties for an anode current collector used in a polymer electrolyte membrane water electrolyzer operated at the boiling point of water, Journal of Power Sources, Volume 332, p. 16-23., 10.1016/j.jpowsour.2016.09.086, 322, 16-23, 2016.11, This study attempts to optimize the properties of the anode current collector of a polymer electrolyte membrane water electrolyzer at high temperatures, particularly at the boiling point of water. Different titanium meshes (4 commercial ones and 4 modified ones) with various properties are experimentally examined by operating a cell with each mesh under different conditions. The average pore diameter, thickness, and contact angle of the anode current collector are controlled in the ranges of 10-35 μm, 0.2-0.3 mm, and 0-120°, respectively. These results showed that increasing the temperature from the conventional temperature of 80 °C to the boiling point could reduce both the open circuit voltage and the overvoltages to a large extent without notable dehydration of the membrane. These results also showed that decreasing the contact angle and the thickness suppresses the electrolysis overvoltage largely by decreasing the concentration overvoltage. The effect of the average pore diameter was not evident until the temperature reached the boiling point. Using operating conditions of 100 °C and 2 A/cm2, the electrolysis voltage is minimized to 1.69 V with a hydrophilic titanium mesh with an average pore diameter of 21 μm and a thickness of 0.2 mm..
6. YanMing 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), 75, 14, 1155-1163, 2016.10, 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..
7. Kohei Ito, Takukya Sakaguchi, Yuta Tuchiya, Akiko Inada, Hironori NAKAJIMA, Ryo Saito, Gas Crossover Suppression by Controlling Wettability of Cathode Current Collector, ECS Transactions, 75 (14) 1107-1112 (2016), 75, 14, 1107-1112, 2016.10, Hydrogen gas crossover, which reduces current efficiency, is critical issue in high pressure PEMWE (Polymer Electrolyte Membrane Water Electrolysis). This study proposes controlled wettability current collector, which enhances the detachment of hydrogen gas bubble from the current collector and decreases the crossover. A high pressure operation of a PEMWE cell with visualization clarified that the wettability impacts on the bubble dynamics and changes the current efficiency. Among the current collectors prepared, hydrophilic one indicated higher current efficiency and suggested smaller crossover..
8. Hua Li, Hironori NAKAJIMA, Kohei Ito, Optimization of annealing catalyst powder for high temperature PEMWE, ECS Transactions, 75 (14) 1095-1105 (2016), 75, 14, 1095-1105, 2016.10, To investigate the impact of annealing conditions on electrolysis performance, annealed IrO2 powders are examined as anode catalysts in a high temperature polymer electrolyte membrane water electrolyzer (PEMWE). The IrO2 powders were annealed for from 1 to 8 hours under 350 oC and 490 oC. The effect of annealing time and temperature on the IrO2 phase, specific surface area of IrO2 and high frequency resistance (HFR) is investigated through analyzing the current-voltage (I-V) characteristics. The experiment result shows that annealing impacts on electrolysis performance majorly through changing IrO2 phase. Both lengthening annealing time and elevating annealing temperature change IrO2 phase from amorphous phase to crystal phase. The optimum annealing conditions is annealing IrO2 powder at 350 oC for 1 hour..
9. H. Anai, J. Matsuda, Z. Noda, Tachikawa Yuya, Akari Hayashi, Kohei Ito, Kazunari SASAKI, Preparation of Iridium/SnO2/VGCF Electrocatalysts for Water Electrolysis, ECS Transactions, 75 (14) 1129-1135 (2016), 75, 14, 1129-1135, 2016.10.
10. 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, Volume 325, 1 September 2016, Pages 229–237, Volume 325, 1 September 2016, Pages 229-237, 2016.09.
11. 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, Journal of Power Sources, Volume 318, 30 June 2016, Pages 192–199, 10.1016/j.jpowsour.2016.03.108, Volume 318, pp.192-pp.199, 2016.06.
12. Hua Li, Akiko Inada, Hironori NAKAJIMA, 伊藤 衡平, Impact of Cathode Current Collector on High Temperature PEM Water Electrolysis, ECS Transactions 69(18), pp.3-12(2015), 10.1149/06918.0003ecst, volume 69, issue 18, pp.3-pp.12, 2015.12, The effect of cathode current collectors on polymer electrolyte membrane water electrolysis (PEMWE) was evaluated with I-V and I-high frequency resistance (HFR) characteristics. Results reveal that cathode current collectors can impact water electrolysis performance by controlling the amount of water accumulation there, which is proved with overpotential analysis and systematic operation such as feeding additional nitrogen gas to cathode. The hydrophilic cathode current collectors invited better performance than hydrophobic ones, because the hydrophilic ones gives less water accumulation there and enough water content in catalyst coated membrane (CCM). The thickness of cathode current collector did not impact the performance..
13. Yusuke Maeda, Takuya Sakaguchi, Shigeru Tsukamoto, Akiko Inada, Yuta Tsuchiya, Hironori NAKAJIMA, 伊藤 衡平, Analysis and visualization of water flow impact on hydrogen production efficiency in solid polymer water electrolyzer under high-pressure condition, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2015.03.045, vol.40, pp.5 9 9 5-pp.6 0 0 3, 2015.04, When a solid polymer water electrolyzer (SPWE) is operated under high-pressure conditions,
a large pressure difference occurs between the anode and cathode. This causes
crossover of produced gas, especially hydrogen gas, leading to a decrease in the production
efficiency of an SPWE. As a countermeasure against gas crossover, water should be supplied
into the cathode channel, as well as into the anode channel, because the water flow
will facilitate the drainage of hydrogen gas outside of the cell, resulting in decreased
crossover and increased efficiency of the SPWE. This countermeasure is evaluated by
observing SPWE operation at a pressure of 2 MPa, with a visualization of hydrogen bubbles
in the cathode channel. The evaluation revealed that supplying water into the cathode
channel increases the efficiency by several percent at 0.33 A/cm2. Further, the visualization
of the hydrogen bubbles revealed an enhancement in the separation of hydrogen bubbles
from the surface of the current supplier. This suggests that additional water flow can increase
the hydrogen production efficiency through promoting bubble detachment..
14. Yoshinori Kobayashi, 立川 雄也, Kohei Ito, Kazunari SASAKI, A Solid Polymer Water Electrolysis System Utilizing Natural Circulation, International Journal of Hydrogen Energy, Volume 39, Issue 29, 2 October 2014, Pages 16263-16274, 2014.10.
15. Kohei Ito, Yusuke Maeda, Impact of Water Flow Rate on Current Efficiency in Solid Polymer Water Electrolyzer Under 2 MPa Condition, ECS Transactions Volume 64, Issue 3, 2014, Pages 1019-1028, 2014.09, When solid polymer water electrolyzer (SPWE) is operated under high pressure conditions, large pressure difference forms between anode and cathode. It causes crossover of produced gas, especially for hydrogen gas, and decreases current efficiency of SPWE. Supplying water into cathode channel, in addition to anode, is a countermeasure to suppress the crossover, because the water flow improves to drain the hydrogen gas outside of cell, resulting in a decrease of the crossover and increase of the efficiency. This countermeasure for the crossover is evaluated by a SPWE operation under 2 MPa condition with visualization of hydrogen bubbles in cathode channel. The evaluation revealed that supplying water into cathode channel increases the efficiency by several percent under 0.33 A/cm2. Enhanced detachment of hydrogen bubbles from the surface of current supplier was confirmed by the visualization. It is suggested that this enhancement increases the efficiency. © The Electrochemical Society..
16. Ryosuke Nagahisa, Daiki Kuriya, Hidetaka Muramatsu, Yasuyuki Takata, Kuniyasu Ogawa, Kohei Ito, Measurement System for Solubility and Self-Diffusivity of Hydrogen Gas Dissolved in Polymer Electrolyte Membrane, Journal of The Electrochemical Society, 161 (10) F1070-F1074 (2014), 10.1149/2.0881410jes, volume 161, issue 10, F1070-F1074, 2014.07, The characteristics of hydrogen gas permeation through a polymer electrolyte membrane (PEM) are important in determining the performance of electrochemical systems such as fuel cells and electrolyzers. However, the only available data related to these characteristics are those for the hydrogen permeability, which were obtained from measurements under a given pressure difference through the PEM. Although we can derive the solubility and self-diffusivity from the permeability, the derivation requires a mathematical procedure, such as providing a gas transport model and fitting experimental data with theoretical data from the model. In this study, we developed a measurement system that uses nuclear magnetic resonance and can quantify both the solubility and self-diffusivity in a rather straightforward manner. The system allows us to measure these two properties when hydrogen gas is dissolved in a dry Nafion membrane under a hydrogen gas pressure of up to 1 MPa at room temperature. The solubility increases linearly with increasing pressure, and the solubility coefficient is (1.3 ± 0.13) × 10−5 mol/(cm3MPa). The self-diffusivity shows a constant value of (2 ± 0.4) × 10−6 cm2/s regardless of the pressure..
17. Yuji Ishikawa, Masahiro Shiozawa, Masaaki Kondo, Kohei Ito, Theoretical analysis of super-cooled state of water generated below the freezing point in a PEFC, International Journal of Heat and Mass Transfer, Vol.74, July 2014, 10.1016/j.ijheatmasstransfer.2014.03.038, July2014, 74, 215-227, 2014.04, The water produced in a proton exchange fuel cell can exist in supercooled states during cold start operation. Visualization studies of unit cells under cold start conditions have confirmed that supercooled states exist in the cells and that they are eventually released. However, these supercooled states have not been quantitatively characterized, and it is difficult to predict them. Moreover, it has not been clarified what determines the supercooling degree and the release of supercooled states in each part of the cells, such as the gas flow channels, gas diffusion layers, and catalyst layer. In this work, a theoretical model was developed to predict the release of supercooled states on the basis of heterogeneous nucleation theory and by considering the surface wettability of the porous media in the cells. This model was evaluated through comparison to our in situ visualization study of a cell during a cold start. The developed model reproduced the supercooled state in the cell well, specifically its release time, and quantitatively clarified the impact of the pore diameter and wettability on the supercooled states.

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18. Kuniyasu Ogawa, Tomoyuki Haishi, Kohei Ito, Differences in Drying/WettingWater Transfer Resistance Through a Platinum Catalyst Layer of a PEMFC Electrode Membrane, Journal of The Electrochemical Society, Journal of The Electrochemical Society, 161 (1) F239-F245 (2014), 2014.01, In order to understand the water transport phenomenon in a membrane electrode assembly (MEA), the water transfer resistance
through a platinum catalyst layers (CL) is required. In this study, the overall water transfer resistance through the CL is taken as the
sum of the resistance to charge/discharge water from the surface of ionomer in the CL and the resistance for water to pass through the
ionomer in the CL. The value of this quantity for a CL that is 4 μm thick and is coated on a 178 μm thick Nafion 117, was estimated.
The MEA was dried/wetted by supplying gas with controlled humidity to the surface of the MEA. The water concentration contained
in the PEM was measured by nuclear magnetic resonance (NMR) using a small detection coil. The rates of drying/wetting of the
MEA were calculated from time-dependent changes of the water concentration measured in the PEM. The overall water transfer
resistance through a CL was estimated by comparing experiment and analytical results based on the analytical model. As a result,
the overall water transfer resistances through the 4 μm thick CL during drying and wetting were 0–3 × 104 and 10 ± 6 × 104 s/m,
respectively.
19. Sang-Kun Lee, Kohei Ito, Cross-Sectional Visualization and Analysis of Droplet Behavior in Gas Flow Channel in PEFC, Journal of The Electrochemical Society, 161 (1) F58-F66 (2014), Journal of The Electrochemical Society, 161 (1) F58-F66 (2014), 2014.01, A new cross-sectional visualization cell in which a transparent material is not embedded in the separator was developed to observe water droplet behavior in a flow channel and to analyze the impact of the channel and gas diffusion layer (GDL) surface on the behavior. A specific GDL and separator pair was chosen so that the surface of the GDL was more hydrophobic than that of the separator, where the contact angle difference between them was approximately 27◦. With this GDL and separator pair, a droplet formed in the channel does not touch the GDL surface. This specific pair also makes the droplet smaller and causes less of a pressure drop through the channel, leading to superior drainage from the channel. A theoretical analysis based on the force balance surrounding a droplet explains this superior drainage. The reason is that the combination of the hydrophobic GDL and hydrophilic
separator reduces the adhesion force on the droplet, promoting water drainage..
20. Kuniyasu Ogawa, Yasuo Yokouchi, Tomoyuki Haishi, Kohei Ito, Development of an eight-channel NMR system using RF detection coils for measuring spatial distributions of current density and water content in the PEM of a PEFC, Journal of Magnetic Resonance Volume 234, 2013, Pages 147-153, 10.1016/j.jmr.2013.06.015, pp. 147-pp. 153, 2013.10, The water generation and water transport occurring in a polymer electrolyte fuel cell (PEFC) can be estimated from the current density generated in the PEFC, and the water content in the polymer electrolyte membrane (PEM). In order to measure the spatial distributions and time-dependent changes of current density generated in a PEFC and the water content in a PEM, we have developed an eight-channel nuclear magnetic resonance (NMR) system. To detect a NMR signal from water in a PEM at eight positions, eight small planar RF detection coils of 0.6 mm inside diameter were inserted between the PEM and the gas diffusion layer (GDL) in a PEFC. The local current density generated at the position of the RF detection coil in a PEFC can be calculated from the frequency shift of the obtained NMR signal due to an additional magnetic field induced by the local current density. In addition, the water content in a PEM at the position of the RF detection coil can be calculated by the amplitude of the obtained NMR signal. The time-dependent changes in the spatial distributions were measured at 4 s intervals when the PEFC was operated with supply gas under conditions of fuel gas utilization of 0.67 and relative humidity of the fuel gas of 70%RH. The experimental result showed that the spatial distributions of the local current density and the water content in the PEM within the PEFC both fluctuated with time..
21. Kohei Ito, Electrochemical Characterization of Hydrogen Pump With Internal Humidifier and Dead-End Anode Channel, ECS Transactions Volume 58, Issue 1, 2013, Pages 681-691, 2013.10, 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..
22. Y. Ishikawa, M. Shiozawa, M. Kondo and Kohei Ito, A Map to Start PEFC under Freezing Temperature-Theoretical Analysis of Super-Cooled State in Cell-, ECS Transactions Volume 50, Issue 2, 2012, Pages 123-135, PEFC12, vol.50, no.2, pp123-136, 2012.10, Efficient cold start of PEFC under freezing point can be realized by keeping the super-cooled state of generated water. If a super-cooled state is maintained, the cell can start under a freezing point with generated heat, and the cell reaches a steady state without the gas-supply block caused by the ice from the generated water. Difficult task, such as a shorter cold-start at a lower temperature, is possible by adequate choice of component material used in the cell, and by active heat generation with a suppressed air supply. Against such a background, this paper discussed which characteristic of the component in cell leads to the success of cold start, namely of keeping super-cooled state during cold start. This analysis was performed on the basis of heterogeneous nucleation theory, which considers the wettability of surface of the component material..
23. Kohei Ito, Design and characterization of high pressure electrochemical hydrogen pump, 19th World Hydrogen Energy Conference2012, 2012.06, Hydrogen energy society, especially hydrogen gas station for FCV, needs stable supply of high pressure hydrogen gas at 40 MPa or more than that. However, conventional booster, which is mechanically driven, has rather low reliability. Against this situation we expect electrochemical booster called as hydrogen pump, where hydrogen gas is pressurized by the immigration of the gas from anode to cathode through DC-applied MEA (membrane electrode assembly). The hydrogen pump is predicted that it has high reliability because of no mechanical links and that it has high efficiency in principle because of isothermal process. Here we show the minimum power of hydrogen pump and the concerns inherently existed in the pump, such as back diffusion of hydrogen gas pumped and breaking of MEA. Moreover, a prototype model of the hydrogen pump up to 2 MPa is designed and fabricated, and voltage and current efficiency obtained from the first running of the pump are presented. .
24. Chiaki Mizutani1, Sungkun Lee2, Isamu Kuroda3 Yusuke Meda1 Kohei Ito1 , 3D temperature distribution in PEFC by a new measurement method with fine thermocouple array
, 8th Thermal and Fluids Engineering Conference, Incheon, Korea, March 18-21, 2012, 2012.03.
25. Kazunari Sasakia, 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, Vol.196, pp.9130-9140, 2011, Vol.196, pp.5377-5385(2011), 2011.11.
26. K. Sasaki, K. Haga, T. Yosizumi, D. Minematsu, E. Yuki, R.R.Liu, C.Uryu, T. Oshima, S Taniguchi, Y Shiratori, and K. Ito, Sulfur Poisoning of SOFCs:Dependence on Operational Parameters , ECSTransactions,35(1),2805-2814, 2011.10.
27. F Takasaki, S Matsuie, Y Takabatake, Z Noda, A Hayashi, Y Shiratori, K. Ito and K.Sasaki , Carbon-Free Pt Electrocatalysts Supported on SnO2 for Polymer Electrolyte Fuel Cells:Electrocatalytic Activity and Durability, J. Electrochem. Soc.,158(10),B1270-B1275, 2011.10.
28. Yosizumi T.,Uryu C.,Oshima T.,Shiratori Y.,Ito K.and Sasaki K., Sulfur Poisoning of SOFCs:Dependence on Operational Parameters , ECSTransactions,35(1),1717-1725, 2011.10.
29. Yonekura T.,Tachikawa Y.,Yoshizumi T.,Shiratori Y.,Ito K.and Sasaki K., Exchange Current Density of Solid Oxide Fuel Cell Electrodes, ECS Transactions 35(1),1007-1014, 2011, 2011.10.
30. Liu,R.R.,Taniguchi S.,Shiratori Y, Ito K.and Sasaki K. , Influence of SO_2 on the Long-term Durability of SOFC Cathodes, ECS Transactions 35(1),2255-2260, 2011, 2011.10.
31. Ryosuke Nagahisa, Daiki Kuriya, Kuniyasu Ogawa, Yasuyuki Takata and Kohei Ito , Measurement of Hydrogen-Gas Solubility and Diffusivity in Polymer Electrolyte Membrane by NMR Method
, ECS Trans. vol.41, pp. 1423-1430(2011), 2011.10.
32. Kohei Ito、Tomoaki Hagio、Akira Matsuo、Yasushi Iwaisako、Osamu Nakabeppu, EXPERIMENTAL ANALYSIS OF THERMAL AND ELECTRIC TRANSPORT CHARACTERISTICS OF NANO-GAPS, Proceedings of the ASME/JSME 2011 8th Thermal Engineering Joint Conference、AJTEC2011 , CD-ROM, 2011.03.
33. 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,Vol.196, pp.5377-5385(2011), Vol.196, pp.5377-5385(2011), 2011.02.
34. Sang-Kun Lee, Kohei Ito, Kazunari Sasaki, A Cross-sectional Observation of Water Behavior in the Flow Channel in PEFC, ESC Transactions, Vol. 33, Issue 1, (2010), 2010.10.
35. Kazunari Sasaki, Fumiaki Takasaki, Zhiyun Noda, Shingo Hayashi, Yusuke Shiratori, Kohei Ito, Alternative Electrocatalyst Support Materials for Polymer Electrolyte Fuel Cells, ESC Transactions, Vol. 33, Issue 1, (2010), 2010.10.
36. Yasuo YOKOUCHI, Kuniyasu OGAWA, Tomoyuki HAISHI and Kohei ITO , Current-Distribution Measurement in Polymer Electrolyte Water Electrolysis Equipment and Polymer Electrolyte Fuel Cell using NMR Sensor, Special Issue on the Second Internatinal Forum on Heat Transfer, Journal of Thermal Science and Technology, Vol.4, No.4, pp.462-468(2009), 2009.12.
37. K. Araki, J. Yamamoto, Y. Shiratori, K. Ito, and K. Sasaki, Performance and Long-term Durability of Nanostructured Ni Anodes Doped with Transition Metals Prepared by Spray Mist Dryer, ECS Transactions, Vol.25, No.2, pp.2039-2048(2009), 2009.10.
38. R. R. Liu, S. H. Kim, Y. Shiratori, T. Oshima, K. Ito, and K. Sasaki, The Influence of Water Vapor and SO2 on the Durability of Solid Oxide Fuel Cells, ECS Transactions, Vol.25, No.2, pp.2859-2866(2009), 2009.10.
39. K. Haga, Y. Shiratori, K. Ito, and K. Sasaki, Chemical Degradation and Poisoning Mechanism of Cermet Anodes in Solid Oxide Fuel Cells, ECS Transactions, Vol.25, No.2, pp. 2031-2038(2009), 2009.10.
40. Sang-Kun Lee, Kohei Ito, and Kazunari Sasaki, Temperature Measurement of Through-plane Direction in PEFC with a Fabricated In-line Thermocouple and Supporter
, ESC Transactions, Vol.25, No.1, pp.495-503(2009), 2009.10.
41. Kohei Ito, Sangkun Lee, Atsushi Yamamoto, Masaaki Hirano, Hidetaka Muramatsu, Kazunari Sasaki and Kuniyasu Ogawa, KEYNOTE PAPER: IN-SITU MEASUREMENT IN THROUGH-PLANE DIRECTION IN PEMFC, Proceedings of the Seventh International ASME Conference on Nanochannels, Microchannels and Minichannels, ICNMM2009-82132(2009), 2009.06.
42. A. Masao, S. Noda, F. Takasaki, K. Ito, and K. Sasaki, Carbon-free Pt Electrocatalysts Supported on SnO2 for Polymer Electrolyte Fuel Cells, Electrochem. Solid-State Lett., Vol.12, No.9, pp.B119-B122(2009), 2009.06.
43. Sang-Kun Lee, Kohei Ito, Toshihiro Ohshima, Shiun Noda, and Kazunari Sasaki, In-situ Measurement of Temperature Distribution across a Proton Exchange Membrane Fuel Cell, Electrochemical and Solid-State Letters, Vol.12, No.9, pp.B126-130(2009), 2009.06.
44. Development of a measurement technique for current-density in PEFC using planar surface coil as a NMR signal detector First report: One-dimensional measurement of current-density generating in PEFC
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45. Numerical analysis of thermoelectric phenomenon by Boltzmann transport equation with discretization of all wave-number spaces.
46. Yasuo Yokouchi, Kuniyasu Ogawa, Tomoyuki Haishi and Kohei Ito, Current-Distribution Measurement in PEFC Using NMR Sensors ; Experimental and Theoretical Results under Uniform Electric Power Generation Condition, Proceedings of the Seventh JSME-KSME Thermal and Fluids Engineering Conference, (2008), 2008.10.
47. K. Haga, Y. Shiratori, K. Ito, and K. Sasaki, Chlorine Poisoning of SOFC Ni-Cermet Anodes, J. Electrochem. Soc., Vol.155, No.12, B1233-B1239 (2008), 2008.09.
48. K. Haga, S. Adachi, Y. Shiratori, K. Ito, and K. Sasaki, Poisoning of SOFC Anodes by Various Fuel Impurities, Solid State Ionics, Vol.179, No.27-32, pp.1427-1431 (2008), 2008.09.
49. Yasuo YOKOUCHI, Kuniyasu OGAWA, Tomoyuki HAISHI and Kohei ITO, CURRENT-DISTRIBUTION MEASUREMENT IN MEMBRANE ELECTRODE ASSEMBLY UNDER WATER
ELECTROLYSIS CONDITION USING NMR SENSOR, Proceedings of the 2nd International Forum on Heat Transfer , pp.94-97(2008), 2008.09.
50. 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, Vol.177, No.2, pp.303-313(2008), 2008.03.
51. 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, Vol.175, No.2, pp.732-738(2008), 2008.01.
52. S. H. Kim, T. Ohshima, Y. Shiratori, K. Ito, and K. Sasaki, Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells, Materials Research Society Symposium Proceedings, Vol.1041, pp131-137 (2007), 2007.11.
53. Kohei Ito, Tomohiko Miyazaki, SangKun Lee, Kazunari Sasaki, Hiromitsu Masuda, Kyushu University, Visualization of flooding in GDL with sectional model cell, 2007 Fuel Cell Seminar and Exposition, San Antonio, Texas, USA, October 15-19, 2007, 2007.10.
54. Kohei Ito, Tomohiko Miyazaki, SangKun Lee, Kazunari Sasaki, Hiromitsu Masuda, Visualization of flooding in GDL with sectional model cell, 2007 Fuel Cell Seminar and Exposition, San Antonio, Texas, USA, October 15-19, 2007, 2007.10.
55. Kuniyasu Ogawa, Tomoyuki Haishi and Kohei Ito, Local water-content measurement of PEM for fuel cell applications using planar surface coils, Proceedings of the 9th ICMRM in Aachen, 2-7 September, 2007, Aachen, Germany
, 2007.09.
56. Kuniyasu OGAWA, Naruhiko SHIRAI, Kohei ITO, Tomoyuki HAISHI, Water-Content Measurement in Polymer Electrolyte Membrane Using MRI for Estimation of Diffusion Coefficient of Water, Proceedings of The 8th Asian Thermophysical Properties Conference, Fukuoka, Japan, No.145(2007), 2007.08.
57. Estimation of flooding in PEMFC gas diffusion layer by differential pressure measurement
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58. Y. Kawasoe, T. Kuroki, H. Kusaba, K. Ito, Y. Teraoka, and K. Sasaki, Preparation and Electrochemical Activities of Pt-Ti Alloy PEFC Electrocatalysts, J. Electrochem. Soc., Vol.154, No.9, pp.B969-B975(2007), 2007.07.
59. Hiromitsu Masuda, Kohei Ito, Toshihiro Oshima, Kazunari Sasaki, Visualization and 2D-2phase numerical simulation on liquid water behavior in a straight channel PEFC, The 5th International Conference on Fuel Cell Science, Engineering and Technology, New York, NY, USA, June 18-20, 2007, 2007.06.
60. K. Sasaki, S. Adachi, K. Haga, M. Uchikawa, J. Yamamoto, A. Iyoshi, J.-T. Chou, and K. Itoh, Fuel Impurity Tolerance of Solid Oxide Fuel Cells, ECS Transactions, Vol.7, No.1, PP.1675-1683(2007), 2007.06.
61. Numerical Analysis of Transient Response in Polymer Electrolyte Membrane Fuel Cell Considering Gas/Liquid Two Phase Flow.
62. Kohei Ito, Hiromitsu Masuda, Tomohiko Miyazaki, Yasushi Kakimoto, 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, Irvine, CA, USA, June 19-21, 2006, 2006.06.
63. 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, Irvine, CA, USA, June 19-21, 2006, 2006.06.
64. Local water-content measurement of polymer electrolyte membrane for fuel cell applications using planar surface coil as a NMR signal detector.
65. K. Ito, H. Masuda, T. Miyazaki, T. Oshima, Y. Kakimoto, Water Problem in Polymer Electrolyte Membrane Fuel Cell, Proceedings of The 3rd Korea-Japan Joint Seminar on Heat Transfer, pp.118-122(2005), 2005.09.
66. Kohei Ito, Hiromitsu Masuda, Tomohiko Miyazaki, Yasushi Kakimoto, Takashi Masuoka, Investigation of Flooding Phenomena in PEMFC by Two-Phase Flow Numerical Simulation, The 3rd International Conference on Fuel Cell Science, Engineering and Technology, 19-24, FUELCELL2005-74170, Yipsilanti, MI, USA, May 22-25, 2005, 2005.05.
67. Kuniyasu Ogawa, Tomoyuki Haishi and Kohei Ito, Development of a local NMR sensor for wetness monitoring of polymer electrolyte membrane using a planar surface coil, Proceedings of 6th World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics, 2-a-2, Matsushima, Miyagi, Japan, 2005.04.
68. Kohei Ito, Ryohei MURAMOTO, Isamu SHIOZAWA, Yasushi KAKIMOTO, Takashi MASUOKA, Numerical Analysis of Electro-thermal Phenomena in Metal by Boltzmann Transport Equation for Electron, InterPACK2005, 2099-2103, San Francisco, CA, USA, July 17-22, 2005, 2005.01.
69. Kazuo Onda, Hironobu Kusunoki, Kohei Ito, Hiroshi Ibaraki, Takuto Araki, Numerical simulation of de-Nox performance by repetitive pulsed discharge when added with hydrocarbons such as ethylene, J. Applied Physics, Vol. 97, pp.023301-8(2005), 2005.01.
70. Numerical simulation of DeNOx performance by repetitive pulsed discharge add by hydrocarbon such as ethylene.
71. Kohei Ito, Hironori Koori, Kazuo Onda, Hiromitsu Masuda, Takashi Masuoka, Transient Response Analysis of Polymer Electrolyte Fuel Cell Considering Equivalent Circuit, Mass and
Heat Conservation, The 2nd International Conference on Fuel Cell Science, Engineering and Technology, Rochester, NY, USA, June 14-16, pp.85-92(2004), 2004.06.
72. Prediction of production power of high-pressure hydrogen by high-pressure water electrolysis.
73. Kohei Ito, Shinzi Miyauchi, Kazuo Onda, Hironori Koori, Hisamitsu Masuda, Transient Response of Polymer Electrolyte Fuel Cell to Rapid Change in Load Current, 1st International Symposium on Micro & Nano Technology, Honolulu, Hawaii, USA, March 14-17, 2004, 2004.03.
74. Transient response analysis of polyer electrolyte fuel cell considering equivalent electric circuit and mass conservation.
75. Kazuo Onda, Hironobu Kusunoki, Kohei Ito, Hiroshi Ibaraki, Numerical Analysis of Repetive Pulsed-discharge de-NOx Process with Ammonia Injection, J. Applied Physics, Vol. 95, No. 8, pp.3928-3935(2004), 2004.01.
76. Kazuo Onda, Takahiro Kyakuno, Kikuo Hattori, Kohei Ito, Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis, J. Power Source, Vol. 132, pp.64-70(2004), 2004.01.
77. Thermal behavior of small nickel/metal hydride battery during rapid charge and discharge cycle.
78. Kazuo Onda, Toru Iwanari, Nobuhiro Miyauchi, Kohei Ito, Takahiro Ohba, Yoshinori Sakaki, Susumu Nagata, Cycle Analysis of Combined Power Generation by Planar SOFC and Gas Turbine Considering Cell Temperature Current Density Distributions, J. Electrochem. Soc., Vol. 150, pp.A1569-A1576(2003), 2003.01.
79. Kazuo Onda, Hisashi Kameyama, Takeshi Kanamoto, Kohei Ito, Experimental Study on Heat Generation Behavior of Small Lithium Ion Secondary Batteries, J. Electrochem. Soc., Vol. 150, pp.A285-A291(2003), 2003.01.
80. Numerical analysis of repetitive pulsed-discharge DeNOx process with ammonia injection.
81. System analysis of planar solid oxide fuel cell combined with gas turbine.
82. Measurement of radical concentration by appearance mass spectrometry at low pressure and pulsed-discharge field.
83. Investigation of water molecule concentration distribution and transport coefficient in solid polymer electrolyte membrane by magnetic resonance imaging.
84. Kohei Ito, Katsuyuki Hagiwara Hiroyuki Nakaura Hidekazu Tanaka, Kazuo Onda, Numerical Analysis of Effects of Electric Field and Pulse Duration on Discharge DeNOx Performance, Electrical Engineering in Japan, Vol. 139, pp1-11(2002), 2002.01.
85. Yoshitaka Inui, Tetsuro Suto, Satoshi Kawai, Kohei Ito, Numerical Simulation of Basic Electrical and Thermal Characteristics of Plannar Solid Oxide Fuel Cell, International Conf. Electrical Engineering, pp.335-340(2002), 2002.01.
86. Zhen-Zhou Su, Kohei Ito, Kazunori Takashima, Shinji Katsura, Kazuo Onda, Akira Mizuno, OH radical generation by atmospheric pressure pulsed discharge plasma and its quantitative analysis by
monitoring CO oxidation, J. Physics D, Applied Physics, No. 35, pp.3192- 3198(2002), 2002.01.
87. Kazuo Onda, Toshio Murakami, Takeshi Hikosaka, Misaki Kobayashi, Ryouhei Notu, Kohei Ito, Performance analysis of Polymer-Electrolyte Water Electrolysis Cell at a Small-Unit Test Cell and Performance Prediction of Large Stacked Cell, J. Electrochem. Soc., Vol. 149,, pp.A1069-A1078(2002), 2002.01.
88. Thermal behavior of nickel-metal hydryde battery during charging cycle.
89. Numerical analysis of polymer electrolyte fuel cell using empirical equations for over potentials.
90. Investigation of water molecule concentration distribution and transport coefficient in solid polymer electrolyte membrane by magnetic resonance imaging.
91. Study on heat generation behavior of small lithium-ion secondary battery.
92. Effect of exhaust gas composition, temperature and pressure on discharge DeNOx performance by numerical analysis.
93. System analysis of planar solid oxide fuel cell combined with gas turbine.
94. Kohei Ito, Katsuyuki Hagiwara Hiroyuki Nakaura, Hidekazu Tanaka, Kazuo Onda, Radical Density Measurement at Low-Pressure Discharge Denitrification by Appearance Mass Spectrometry, Jpn. J. Appl. Phys, Vol. 40, pp1472-1476(2001), 2001.01.
95. Performance predection of large stack cell of polymer electrolyte water electrolysis.
96. Measurement and discharge-chemical kinetics calculation of radical density at low-pressure discharge denitrification.
97. Kohei Ito, Kuniyasu Ogawa, Investigation of Water Molecule Distribution and Transport Mechanism in Polymer Electrolyte Membrane by Magnetic Resonance Imaging, Proceeding of the 4th JSME-KSME Thermal Engineering Conference, October 1-6, 2000, Kobe, Japan, Vol. 3, pp355-360(2000), 2000.01.
98. Mitsunori Iwata, Takeshi Hikosaka, Makoto Morita, Toru Iwanari, Kohei Ito, Onda Kazuo, Yoshimi Esaki, Performance analysis of Planar-type unit SOFC considering current and temperature distributions, Solid State Ionics, Vol. 132, pp297-308(2000), 2000.01.
99. Makoto Morita, Kohei Ito, Tetsuya Aoki, Tetsuro Suto, Sinzi Miyauchi, Yoshitaka Inui Kazuo Onda, Transient Response of Polymer Electrolyte Fuel Cell for Change of Load Current and Reactant Gas Flow Rate, International Symposium on Fuel Cell for Vehicles in 41st Battery Sym. Jpn., pp.66-67(2000), 2000.01.
100. Measurement and numerical analysis of current density distribution in polymer-electrolyte water electrolysis cell.
101. Ultrasonic irradiating effect on lithium ion secondary battery, polymer electrolyte fuel cell and solid polymer water electrolysis.
102. Numerical analysis of effects of electric field and pulse duration on discharge DeNOx performance.
103. System efficiency of high-temperature water electrolysis by planar solid oxide electrolysis cell.
104. K. Ito, K. Hijikata, Nonequilibrium Effect on Thermoelectric Voltage at Point Contacts, Thermal Science and Engineering, Vol. 3, pp 91-94(1995), 1995.01.
105. Kohei Ito, Kunio Hijikata, Kunikazu Torikoshi, Patrick E. Phelan, Thermoelectric Voltage at Metallic Point Contact by Non-Equilibrium Effectand Electron Tunneling Effect, JSME/ASME Joint Conference at Hawaii, pp.475-482(1995), 1995.01.
106. K.Ito, K. Hijikata, K. Torikoshi, P.E. Phelan, Thermoelectric Voltage at Metallic Point Contacts from Non-Equilibrium Effects, Thermal Science and Engineering, Vol. 3, pp 91-94(1995), 1995.01.
107. Thermoelectric voltage at metallic point contact by nonequilibrium effect and electron tunneling effect.
108. P. E. Phelan, Y. Song, O. Nakabeppu, K.Ito, K. Hijikata, T. Ohmori, K. Torikoshi, Film/Substrate Thermal Boundary Resistance for an Er-Ba-Cu-O High-Tc Thin Film, J. Heat Transfer, Vol.116, pp.1038-1041(1994), 1994.01.
109. Thermoelectric voltage at point contacts by electron tunneling effect.
110. P.E.Phelan, O.Nakabeppu, K.Ito, K.Hijikata, T.Ohmori, K.Torikoshi, Heat Transfer and Thermoelectric Voltage at Metallic Point Contacts, J. Heat Transfer, Vol.115, pp.757-762(1993), 1993.01.
111. K. Hijikata, K. Ito, O. Nakabeppu, P.E. Phelan, K. Torikoshi, Heat and Electron Transport at Point Contacts, The Japan-U.S. Seminar on Molecular and Microscale Heat Transport Phenomena, (1993), 1993.01.
112. P. E.Phelan, O. Nakabeppu, K. Ito, K. Hijikata, T. Ohmori, Film/Substrate Thermal boundary Resistance for an Er-Ba-Cu-O High-Tc Superconducting Film, The Winter Annual Meeting of ASME, Anaheim, California, HTD-Vol.229, pp.33-38(1992), 1992.01.
113. P. E. Phelan, O. Nakabeppu, K. Ito, K. Hijikata, T. Ohmori, K. Torikoshi, Heat Transfer and Thermoelectric Voltage at Metallic Point Contacts, 28th National Heat Transfer Conference and Exhibition, San Diego, HTD-Vol.200, pp.63-69(1992), 1992.01.
114. P.E.Phelan, K.Ito, K.Hijikata, T.Ohmori, Thermal Resistance of Metallic Point Contacts, 3nd World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, pp.1688-1695(1993), 1993.01.