九州大学 研究者情報
論文一覧
伊藤 衡平(いとう こうへい) データ更新日:2023.11.22

教授 /  工学研究院 機械工学部門 水素利用工学


原著論文
1. Linjun Li, Hironori Nakajima, Kohei Ito, Boiling effect on oxygen evolution reaction -Theoretical analysis of its mass transfer enhancement mechanism-, International Journal of Hydrogen Energy, 2023.11.
2. Wei Xuesong, Takumi Kakimoto, Yutaro Umehara, Hironori Nakajima, Kohei Ito, Hiromitsu Inagaki, Shoji Mori, Improvement of the critical current density of alkaline water electrolysis based on the hydrodynamic similarity between boiling and water electrolysis, International Journal of Heat and Mass Transfer, Vol. 214, 124420, 2023, 2023.11, Since water electrolysis is a pollution-free and economical method to produce
hydrogen which has a great potential as an energy carrier, it is imperative to improve
the performance of water electrolysis for efficient hydrogen production. Supposing that
the analogy between boiling and water electrolysis holds, the next interesting question
is whether the water electrolysis performance can also be significantly improved by
using a method that improves the heat transfer coefficient and the critical heat flux
(CHF). The critical current density (CCD), which is the upper operation limit of water
electrolysis, is considered to be one of the keys for effective hydrogen generation.
However, the study on the enhancement of CCD has rarely been conducted. It is
known that the boiling CHF can be improved by a honeycomb porous plate (HPP) due
to two effects, capillary force and path separation of gas-liquid. In this work, we applied
a cooling method using an HPP which has succeeded in improving the boiling CHF to
alkaline water electrolysis. For the first time, we have succeeded in improving the CCD
to approximately 1.3 times (CCD: 6.6 A/cm2) compared to without capillary force case
(CCD: 5.1 A/cm2). As regards the mechanism, the effect of the liquid supply by
capillary action and the improvement of the bubble discharge by separating the
gas–liquid flow path using the honeycomb structure of the HPP play an important role
in increasing the CCD..
3. Xuefeng Wang, Hironori Nakajima, Yoshihiro Iwanaga, Kohei Ito, Numerical and Experimental Investigation of a Cathode-Supported Microtubular Solid Oxide Electrolysis Cell from Current and Temperature Variations In-Situ Assessed with Electrode-Segmentation Method, Journal of Energy Storage, Volume 72, Part C, 25 November 2023, 108459, 2023.11, The electrode segmentation method has been applied to experimentally assess the current and temperature distributions in a cathode-supported microtubular solid oxide electrolysis cell (mt-SOEC). A detailed three-dimensional SOEC model considering the mass/momentum/charge/energy transfer is also developed to explain the in-situ working mechanism with spatial current and temperature variations considering the electrochemical performance and degradation. Both the experimental and numerical results reveal that the electrode-segmentation method exhibits notable nonuniform current and temperature distributions among the segments (up-, mid-, and downstream). Reactant starvation in the mid- and downstream regions leads to spatial current and temperature variations, with the largest temperature gradient observed and predicted between the up- and midstream regions. Further analysis of the temperature variations indicates that endothermic electrochemical Peltier heat in the air (oxygen) electrode (anode) is the primary cause of temperature decrease from 1.0 V to 1.3 V, while heat production with the overpotentials in the fuel (hydrogen) electrode (cathode) dominates temperature increase above 1.3 V..
4. Linjun Li, Hironori Nakajima, Atsushi Moriyama, Kohei Ito, Theoretical analysis of the effect of boiling on the electrolysis voltage of a polymer electrolyte membrane water electrolyzer (PEMWE), Journal of Power Sources 575 (2023) 233143, https://doi.org/10.1016/j.jpowsour.2023.233143, 2023.05.
5. Yusuke Honsho, Mayumi Nagayama, Junko Matsuda, Kohei Ito, Kazunari Sasaki, Akari Hayashi, Durability of PEM water electrolyzer against wind power voltage fluctuation, Journal of power sources, Volume 564, 30 April 2023, 232826, https://doi.org/10.1016/j.jpowsour.2023.232826, 2023.04, The durability of a water electrolysis cell against wind power voltage fluctuations was evaluated by developing an accelerated potential fluctuation test protocol based on wind power voltage fluctuations over an actual 24 h period of operation. Accelerating potential protocol tests corresponding to 160 d of actual operation were performed. The current loss during the test is mostly recovered if rest time was included during the operation. Reversible loss is most likely related to gas stagnation, suppression of oxygen reduction reaction activity owing to the formation less active Ir(V) species, and suppression of gas evolution owing to the increased hydrophilic surface. This irreversible loss can be attributed to the dissolution of IrO2 and the loss of Nafion® ionomer. Even though the potential fluctuation itself was not a problem if the lowest potential was 1.0 V, the upper limit of the potential was rather problematic. When the upper potential is increased to 2.3 V, the oxidation of IrO2 is enhanced, leading to the partial dissolution of IrO2, followed by the formation of a dense structure, a decrease in the oxygen evolution reaction activity, and an increase in the surface hydrophilicity..
6. Ngo Phi Manh, Karimata Takahiro, Saitou Tomoko, Ito Kohei., Effect of current density on membrane degradation under the combined chemical and mechanical stress test in the PEMFCs, Journal of Power Sources, Volume 556, 2023, 232446, https://doi.org/10.1016/j.jpowsour.2022.232446, 2023.02.
7. Yingtian Chi, Kentaro Yokoo, Hironori Nakajima, Kohei Ito, Jin Lin, Yonghua Song, Optimizing the Homogeneity and Efficiency of a Solid Oxide Electrolysis Cell Based on Multiphysics Simulation and Data-driven Surrogate Model, Journal of power sources, Vol. 562, (2023), 232760, 2023.01.
8. Manh Phi Ngo; Hironori Nakajima; Tomoko Saitou; Takahiro Karimata; Kohei ITO, Investigation of in-situ catalytic combustion in polymer-electrolyte-membrane fuel cell during combined chemical and mechanical stress test , Journal of Power Source, 2022.08, Novel catalyst-integrated gas diffusion electrodes (GDEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are
presented, in which porous titanium microfiber sheets are etched in NaOH to generate a nanostructured TiO2 surface, followed by
arc plasma deposition (APD) of iridium nanoparticles. The porous titanium sheet acts as a gas diffusion layer (GDL); the
nanostructured TiO2 surface acts as a catalyst support with large surface area; and the iridium nanoparticles act as the
electrocatalyst. The performance of these unique GDEs in PEMWE cells was optimized by etching in different NaOH
concentrations to vary the nanostructure of the TiO2; and by varying the Ir loading via the number of APD pulses. The currentvoltage characteristics and the durability of the optimized GDEs were comparable to those reported in the literature using
conventional Ir-based electrocatalysts, and electrolysis was achieved with current density up to 5 A cm−2
. The main advantages of
this catalyst-integrated GDE include the very low iridium loading (i.e. around 0.1 mg cm−2
, or just one-tenth of the loading
typically used in conventional PEMWEs); high electrolysis current density; the fabrication of stacks with fewer components; and
the fabrications of thinner stacks. This could ultimately lead to smaller and lower cost PEMWE systems..
9. Linjun Li, Takahiro Karimata, Akari Hayashi, KoheiIto, Evaluation of the boiling effect on oxygen evolution reaction using a three-electrode cell, International Journal of Hydrogen Energy, 2022.06, Novel catalyst-integrated gas diffusion electrodes (GDEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are
presented, in which porous titanium microfiber sheets are etched in NaOH to generate a nanostructured TiO2 surface, followed by
arc plasma deposition (APD) of iridium nanoparticles. The porous titanium sheet acts as a gas diffusion layer (GDL); the
nanostructured TiO2 surface acts as a catalyst support with large surface area; and the iridium nanoparticles act as the
electrocatalyst. The performance of these unique GDEs in PEMWE cells was optimized by etching in different NaOH
concentrations to vary the nanostructure of the TiO2; and by varying the Ir loading via the number of APD pulses. The currentvoltage characteristics and the durability of the optimized GDEs were comparable to those reported in the literature using
conventional Ir-based electrocatalysts, and electrolysis was achieved with current density up to 5 A cm−2
. The main advantages of
this catalyst-integrated GDE include the very low iridium loading (i.e. around 0.1 mg cm−2
, or just one-tenth of the loading
typically used in conventional PEMWEs); high electrolysis current density; the fabrication of stacks with fewer components; and
the fabrications of thinner stacks. This could ultimately lead to smaller and lower cost PEMWE systems..
10. Masahiro Yasutake, Daiki Kawachino, Zhiyun Noda, Junko Matsuda, Stephen M. Lyth,Kohei Ito,Akari Hayashi, and Kazunari Sasaki, Catalyst-Integrated Gas Diffusion Electrodes for Polymer Electrolyte Membrane Water Electrolysis: Porous Titanium Sheets with Nanostructured TiO2 Surfaces Decorated with Ir Electrocatalysts, Journal of The Electrochemical Society, 2020 167 124523, DOI: 10.1149/1945-7111/abb37d, 2020.10, Novel catalyst-integrated gas diffusion electrodes (GDEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are
presented, in which porous titanium microfiber sheets are etched in NaOH to generate a nanostructured TiO2 surface, followed by
arc plasma deposition (APD) of iridium nanoparticles. The porous titanium sheet acts as a gas diffusion layer (GDL); the
nanostructured TiO2 surface acts as a catalyst support with large surface area; and the iridium nanoparticles act as the
electrocatalyst. The performance of these unique GDEs in PEMWE cells was optimized by etching in different NaOH
concentrations to vary the nanostructure of the TiO2; and by varying the Ir loading via the number of APD pulses. The currentvoltage characteristics and the durability of the optimized GDEs were comparable to those reported in the literature using
conventional Ir-based electrocatalysts, and electrolysis was achieved with current density up to 5 A cm−2
. The main advantages of
this catalyst-integrated GDE include the very low iridium loading (i.e. around 0.1 mg cm−2
, or just one-tenth of the loading
typically used in conventional PEMWEs); high electrolysis current density; the fabrication of stacks with fewer components; and
the fabrications of thinner stacks. This could ultimately lead to smaller and lower cost PEMWE systems..
11. Yuto Wakita; Yuya Tachikawa; Hironori Nakajima; Shigeru, Hamada; Kohei Ito, Visualization and mechanical strength of glass seal in planar type solid oxide fuel cells,, Int. J. Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2020.05.153, 2020.06.
12. Jyunya Kai, Ryo Saito, Kenji Terabaru, Hua Li, Hironori Nakajima, Kohei Ito, Effect of Temperature on the Performance of Polymer Electrolyte Membrane Water Electrolysis: Numerical Analysis of Electrolysis Voltage Considering Gas/Liquid Two-Phase Flow, Journal of The Electrochemical Society, 166 (4) F246-F254 (2019), DOI: 10.1149/2.0521904jes, 2019.03, The numerical analysis conducted in this study proposes a guideline to maximize the high-temperature effect, which is expected to
reduce the electrolysis voltage of the polymer electrolyte membrane water electrolyzer. High-temperature operation is intuitively
thought to reduce activation overvoltages. However, a further consideration predicts that high temperature, especially a temperature
higher than the saturated temperature regulated in the operation pressure, decreases the liquid saturation and causes shortage of water,
leading to a large increase in overvoltages. This high temperature problem is analyzed using the developed theoretical model, which
considers gas/liquid behavior. The analysis suggests that, if the gas saturation in the anode catalyst layer is kept at or below 0.3 by
increasing the pressure, liquid water in the catalyst layer is sufficient to OER catalytic ability regulated by exchange current density,
demonstrating that the high-temperature effect works. According to this guideline, increasing the temperature with pressurization
can monotonically reduce the anode activation overvoltage. For instance, raising the temperature from 100 to 120°C and raising the
pressure from 0.13 to 0.22 MPa can prevent the gas saturation from increasing beyond 0.3 and allows the lower electrolysis voltage
to vary from 1.57 to 1.51 V..
13. Yang Ming Hao, Hironori Nakajima, Akiko Inada, Kazunari Sasaki, Kohei Ito, Overpotentials and reaction mechanism in electrochemical hydrogen pumps, Electrochimica Acta 301 (2019) 274e283, DOI: 10.1149/2.0521904jes, 2019.03.
14. Ozgu¨r Aydın, Tatsuhiro Ochiai, Hironori Nakajima, Tatsumi Kitahara, Kohei Ito, Yusuke Ogura, Jun Shimano, Mass transport limitation in inlet periphery of fuel cells: Studied on a planar Solid Oxide Fuel Cell, International Journal of Hydrogen Energy, Vol.43, No.36, (2018), pp.17420-17430, https://doi.org/10.1016/j.ijhydene.2018.07.030, 2018.08, [URL], It was recently clarified on a microtubular Solid Oxide Fuel Cell (SOFC) that the range of
mass transport limitation might commence from the inlet periphery (inlet opening and
inlet pipe), i.e., the concentration gradient of reactants may extend inward the inlet periphery.
For demonstrating that this phenomenon occurs regardless of the form and type of
the fuel cell operating at high reactant utilization rate, herein we investigate the mass
transport in the anode side of a one-cell stack of a planar SOFC. The investigation leans
upon experimental and numerical data analyzed from both conventional (non spatial) and
spatial perspectives. The experimental data were spatially obtained in the lateral direction
by applying the segmentation method. Regarding analyses let us to confirm that mass
transport limitation occurs in the inlet periphery of the planar stack. Besides, the critical
ratio of the consumed/supplied mass fluxes of hydrogen is valid for assessing whether the
concentration gradient of hydrogen extends inward the inlet periphery. Furthermore, the
virtual inlet opening is useful for accurately calculating the mass transport within the active
field of the stack via hypothetically preventing the mass transport limitation in the inlet
periphery. These findings are expected to help researchers and engineers for accurately
designing and characterizing fuel cell systems at varying scales from cells to stacks..
15. 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, [URL], 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..
16. 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..
17. 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.
18. 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), 2017.05.
19. 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..
20. 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..
21. 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..
22. 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..
23. 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.
24. 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.
25. 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.
26. 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..
27. 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..
28. 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, 10.1299/transjsme.2014tep0364, Vol.80, No.820, TEP0364, 2014.12, Local water behaviors in a PEFC was analyzed by equivalent electric circuit and the temperature distribution with an ultra-fine thermocouples. The thermocouple is tailor-made: thermocouple elements in 50 m diameter are welded, and electrically insulated with polyimide coating, resulting in the ultra-fine thermocouple. The temperature distribution, which was measured by the thermocouple placed in array configuration, reveals that the cathode catalyst layer shows the highest temperature in the through-plane direction due to the activation over-potential in cathode. Under low humidification condition, however, the anode catalyst layer has the highest temperature triggered by dried polymer electrolyte membrane and increased IR loss. Along gas flow direction, upstream has the highest temperature, because water droplets accumulate in downstream resulting that load current and heat production concentrates in the upstream. In comparison of the temperature in the adjacent channels direction, the tendency of liquid water accumulation under rib makes the temperature under the channel higher..
29. 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.
30. 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..
31. 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..
32. 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.

.
33. 小川邦康, 横内康夫, 拝師智之, Kohei Ito, 核磁気共鳴を利用した小型表面コイルによる PEFC 内の電流分布計測法の開発
(第3報:PEFC 積層方向に流れる電流分布の逆解析法), 日本機械学会論文集Vol.80, No.812, 2014, [DOI: 10.1299/transjsme.2014tep0093, 2014.04, In the second report, a method for measuring the spatial distribution of the electric current generated in a PEFC from the frequency shift of the Nuclear Magnetic Resonance (NMR) signal of water acquired by eight planar surface coils inserted into the PEFC was described. In this paper, a newly-developed technique to calculate the current density distribution from the measured frequency shifts using inversion analysis is presented. In this technique, the PEFC is divided into eight elements, and the current which flows through the eight elements is searched so that the frequency shift calculated by magnetic field
analysis and the frequency shift obtained by experiment come into agreement. In order to shorten the computation time
consumed in this technique, an efficient algorithm was developed in which the current is searched by an iterative calculation
using the equation between that relates the current and the spatial gradient of the frequency shift. The spatial distribution of
the current density could be obtained using eight iterations of the inversion analysis algorithm..
34. 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.
35. 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..
36. 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..
37. 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..
38. 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..
39. 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. .
40. 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.
41. 横内 康夫, 小川 邦康, 拝師 智之, 伊藤 衡平, 核磁気共鳴法を用いた小型表面コイルによる燃料電池内電流密度および固体高分子膜内含水量の空間分布と時間変化の計測(第二報:燃料ガスの相対湿度と利用率が電流密度分布に及ぼす影響) , 日本機械学会論文集B編 , Vol. 78(2012) No. 788, P928-938, 2012.03.
42. 横内 康夫, 小川 邦康, 拝師 智之, 伊藤 衡平, 核磁気共鳴法を用いた小型表面コイルによる燃料電池内電流密度および固体高分子膜内含水量の空間分布と時間変化の計測(第一報:燃料ガスの相対湿度と利用率がPEM内含水量に及ぼす影響) , 日本機械学会論文集B編 , Vol. 78(2012) No. 788, P917-927, 2012.03.
43. 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.
44. 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.
45. 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.
46. 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.
47. 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.
48. 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.
49. 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.
50. 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.
51. 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.
52. 小川 邦康,横内 康夫,拝師 智之,伊藤 衡平, 核磁気共鳴を利用した小型表面コイルによるPEFC 内の電流分布計測法の開発(第2報:PEFC 積層方向に電流が流れる場合での一次元電流分布の計測), 日本機械学会論文集B編, Vol.76, No.772、pp.216-217(2010), 2010.12.
53. 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.
54. 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.
55. 小川邦康、拝師智之、伊藤衡平, NMR計測における小型表面コイルのレーストラック形状化による信号強度の向上
, 日本機械学会論文集B編, Vol. 76,pp.168-177(2010), 2010.08.
56. 小川邦康、拝師智之、伊藤衡平, 小型NMRセンサーによる高分子電解質膜中でのメタノールの濃度差拡散係数の計測-第一報:計測法の開発と測定値の評価, 日本機械学会論文集B編, Vol.76, No.765、pp.168-177(2010), 2010.05.
57. 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.
58. 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.
59. 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.
60. 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.
61. 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.
62. 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.
63. 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.
64. 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.
65. 横内 康夫, 小川 邦康, 拝師 智之,伊藤 衡平, 核磁気共鳴を利用した小型表面コイルによるPEFC内の電流分布計測法の開発 第一報:PEFC発電時の一次元電流分布の計測
, 日本機械学会論文集B編, Vol.75, No.752, pp.839-846(200), 2009.04.
66. 伊藤衡平、邑本亮平、三木貴文, 波数空間を全て離散化したボルツマン輸送方程式による熱・電気現象の数値解析, 日本機械学会論文集B編, Vol.75, No.749, pp.140-145(2009), 2009.01.
67. 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.
68. 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.
69. 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.
70. 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.
71. 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.
72. 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.
73. 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.
74. 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.
75. 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.
76. 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.
77. 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.
78. 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, Vol.73, No.7, pp.1556-1561(2007), 2007.07.
79. 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.
80. 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.
81. 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.
82. 益田啓光,伊藤衡平,柿本益志,佐々木一成, 気液二相流を考慮した数値シミュレーションによる固体高分子形燃料電池の過渡応答時の解析, 日本機械学会論文集B編, Vol.73, No.3, pp.855-862(2007), 2007.03.
83. 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.
84. 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.
85. 小川邦康、伊藤衡平、拝師智之、菱田公一, 小型表面コイルを用いた燃料電池用固体高分子電解質膜の局所含水量測定法, 日本機械学会論文集B編, Vol.72, No.716, pp.1013-1020(2006), 2006.04.
86. 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.
87. 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.
88. 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.
89. 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.
90. 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.
91. 楠 博敦, 茨木広, 伊藤衡平, 荒木拓人, 恩田和夫, エチレンなどの炭化水素を添加したパルス放電脱硝特性の解析, 電気学会論文誌B, Vol. 125, No. 2, pp.191-198(2005), 2005.01.
92. 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.
93. 客野貴広, 服部紀公士, 伊藤衡平, 恩田和夫, 高圧水電解による高圧水素の製造動力の推定, 電気学会論文誌B, Vol. 124, No. 4, pp.605-611(2004), 2004.04.
94. 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.
95. 伊藤衡平, 宮内伸仁, 恩田和夫, 郡央任, 電気的等価回路と質量保存則を考慮した固体高分子形燃料電池の過渡特性の解析, 電気学会論文誌B, Vol. 124, No. 3, pp.485-495(2004), 2004.03.
96. 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.
97. 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.
98. 影目樹亮, 大嶋孝昌, 中山正人, 伊藤衡平, 恩田和夫, 小型ニッケル水素電池の急速充放電時の発熱挙動, 機械学会論文誌B編, Vol. 70, No. 689, pp.223-228(2004), 2004.01.
99. 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.
100. 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.
101. 楠博敦, 伊藤衡平, 恩田和夫, アンモニアを添加した繰り返しパルス放電脱硝過程の数値解析, 電気学会論文誌B, Vol. 123, No. 12, pp.1546-1553(2003), 2003.01.
102. 岩成亨, 宮内伸仁, 伊藤衡平, 恩田和夫, 榊嘉範, 永田進, 平板型固体酸化物燃料電池とガスタービン複合発電のサイクル計算, 電気学会論文誌B, Vol. 123, pp.683-690(2003), 2003.01.
103. 伊藤衡平, 中浦裕之, 漆畑正太, 恩田和夫, 低圧力、パルス放電条件下での出現質量分析法によるラジカル濃度の測定, 電気学会論文誌, Vol. 122-B, pp.1429-1436(2002), 2002.12.
104. 伊藤衡平, 小川邦康, 磁気共鳴画像法による固体高分子電解質膜内の水分子の濃度分布測定と輸送係数の算出, 日本機械学会論文集B, Vol. 68, pp.543-549(2002), 2002.01.
105. 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.
106. 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.
107. 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.
108. 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.
109. 藤岡陽一, 伊藤衡平, 影目樹亮, 恩田和夫, 大島孝昌, ニッケル水素二次電池の充電時の発熱挙動, 電気学会論文誌, Vol. 122-B, pp.1417-1423(2002), 2002.01.
110. 青木哲也, 宮内伸仁, 村田雅則, 恩田和夫, 乾義尚, 伊藤衡平, 過電圧整理式を考慮した固体高分子燃料電池の特性解析, 電気学会論文誌, Vol. 122-B, pp.1437-1445(2002), 2002.01.
111. 伊藤衡平, 小川邦康, 磁気共鳴画像法による固体高分子電解質膜内の水分子の濃度分布測定と輸送係数の算出, 日本機械学会論文集B, Vol. 68, pp.543-549(2002), 2002.01.
112. 亀山寿, 花本武史, 伊藤衡平, 乾義尚, 恩田和夫,, 小型リチウムイオン二次電池の発熱挙動の研究, 電気学会論文誌, Vol. 122-B, pp.1192-1199(2002), 2002.01.
113. 伊藤衡平, 萩原勝幸, 中浦裕之, 恩田和夫, 田中秀和, 排ガス組成、温度、圧力が放電脱硝性能に及ぼす効果の数値解析, 電気学会論文誌, Vol. 122-B, pp.216-222(2002), 2002.01.
114. 岩成亨, 宮内伸仁, 恩田和夫, 伊藤衡平, 榊嘉範, 永田進, 平板型固体酸化物燃料電池とガスタービン複合発電のサイクル計算, 日本機械学会論文集B, Vol. 68, pp.2664-2670(2002), 2002.01.
115. 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.
116. 村上敏夫, 野津良平, 恩田和夫, 伊藤衡平, 大型固体高分子水電解セルの性能予測, 電気学会論文誌, Vol.121-B, pp475-480(2001), 2001.01.
117. 萩原勝幸, 恩田和夫, 中浦裕之, 伊藤衡平, 田中秀和, 放電脱硝におけるラジカル密度の低圧力場での測定と放電化学反応計算, 日本機械学会論文集B, Vol. 67, pp.2340-2346(2001), 2001.01.
118. 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.
119. 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.
120. 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.
121. 村上敏夫, 彦坂猛, 荒永忠生, 恩田和夫, 伊藤衡平, 固体高分子水電解セルの電流密度分布の測定と数値解析, 電気学会論文誌, Vol. 120-B, pp.256-263(2000), 2000.01.
122. 伊藤衡平, 萩原勝幸, 中浦裕之, 恩田和夫, 田中秀和, 電界とパルス幅が放電脱硝性能に与える効果の数値解析, 電気学会論文誌, Vol. 120-A, pp979-986(2000), 2000.01.
123. 彦坂猛, 岩田三徳, 恩田和夫, 伊藤衡平, 永田進, 平板型固体電解質セルによる高温水蒸気電解システムの電気効率, 電気学会論文誌, Vol. 120-B, pp694-703(2000), 2000.01.
124. 角谷俊次, 松本通弘, 彦坂猛, 富家俊光, 伊藤衡平, 恩田和夫, 佐藤正典, リチウムイオン二次電池や固体高分子燃料電池、固体高分子水電解に対する超音波照射効果, 電気学会論文誌, Vol.199-B, pp.635-636(1999), 1999.01.
125. K. Ito, K. Hijikata, Nonequilibrium Effect on Thermoelectric Voltage at Point Contacts, Thermal Science and Engineering, Vol. 3, pp 91-94(1995), 1995.01.
126. 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.
127. 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.
128. 土方邦夫, 伊藤衡平, 鳥越邦和, 金属点接触における非平衡効果及び電子トンネル効果による熱起電力, 日本機械学会論文集B, Vol. 61, pp.1863-1868(1995), 1995.01.
129. 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.
130. 土方邦夫, 伊藤衡平, 中別府修, Patrick E. Phelan, 鳥越邦和, 点接触における電子トンネル効果の熱起電力, 日本機械学会論文集B, Vol. 60, pp.2171-2175(1994), 1994.01.
131. 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.
132. 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.
133. 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.
134. 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.
135. 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.

九大関連コンテンツ

pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。