Daiki Ataka Engineering Co.

Osaka, Japan

Daiki Ataka Engineering Co.

Osaka, Japan
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Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | Nakano A.,Japan National Institute of Advanced Industrial Science and Technology | Kato A.,Takasago Thermal Engineering Co. | Yoshida T.,Daiki Ataka Engineering Co.
Electrochimica Acta | Year: 2013

The effect of pore structural properties (porosity and pore diameter) of current collectors in proton exchange membrane (PEM) electrolyzers on electrolysis performance was experimentally evaluated by using various titanium (Ti)-felt substrates with different porosities and pore diameters (measured by capillary flow porometry) as the anode current collectors. The current-potential (j-ΔV) characteristics were measured, and overpotential analysis was performed based on the j-ΔV characteristics and the cell resistance (Rcell) data. The results showed that (1) the effect of the decrease in water supply on the membrane resistance due to produced gas bubbles is limited when the mean pore diameter of the anode current collector is less than 50 μm, but might appear at the concentration overpotential, and (2) enhancing the uniform and sufficient contact between the current collector and the electrode reduces not only the contact resistance but also the activation overpotential. © 2012 Elsevier Ltd.


Hwang C.M.,Japan National Institute of Advanced Industrial Science and Technology | Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | Nakano A.,Japan National Institute of Advanced Industrial Science and Technology | And 2 more authors.
ECS Transactions | Year: 2012

Unitized reversible fuel cells (URFC) combine the functionality of a fuel cell and electrolyzer in one unitized device. Proper water management in URFC is critical to achieve better performance. The flow channel design is directly related to this water management because supplied and discharged water through the flow channels of bipolar plates is essential for not only fuel cell operation but also electrolysis operation. The purpose of this research was to find out an effective flow field design. An experimental testing has been conducted to investigate the effects of different flow field design (parallel, serpentine-single, and serpentine-dual) to the URFC performance. And bare Ti-felt GDL and PTFE treated (10 wt.% emulsion) Ti-felt GDL are tested in the oxygen electrode of URFC. The polarization curve has been obtained and it is analyzed. The experimental result shows that the parallel and serpentine-dual flow types provide the better fuel cell performance and electrolysis performance when they are consist with PTFE treated Ti-felt GDL, whereas serpentine-single shows fuel cell performance degradation even though water electrolysis performance is improved. © The Electrochemical Society.


Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | Nakano A.,Japan National Institute of Advanced Industrial Science and Technology | Hwang C.M.,University of Tsukuba | And 3 more authors.
International Journal of Hydrogen Energy | Year: 2012

Experimental study on proton exchange membrane (PEM) electrolyzer was carried out focusing on the effect of pore structural properties of current collectors, such as porosity and pore diameter. Various titanium (Ti)-felt substrates with different porosities and pore diameters (measured by capillary flow porometry) were used as the anode current collector. Results show that when the mean pore diameter of the current collector was larger than 10 μm, the electrolysis performance improved with decreasing pore diameter. In contrast, changes in porosity had no significant effect on the cell performance when the porosity exceeded 0.50. The flow pattern of two-phase flow in the flow channel was discussed in terms of its relationship to bubble size and to pore diameter of the current collector. Finally, correlation between the calculated membrane resistance and the measured pore diameter of the current collectors suggest that larger bubbles generated from larger pores tend to become long bubbles in the channel, thus hindering the water supply to the membrane. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Hwang C.M.,University of Tsukuba | Ishida M.,University of Tsukuba | Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | And 3 more authors.
Journal of Power Sources | Year: 2012

Polymer electrolyte-based unitized reversible fuel cells (URFCs) can be operated either as an electrolyzer to split water into hydrogen and oxygen using electric power or as a fuel cell to supply electric power when fed hydrogen and oxygen or air. In a URFC, titanium (Ti)-felt is used as a gas diffusion layer (GDL) in the oxygen electrode and typical carbon paper is used as a GDL in the hydrogen electrode. Here, first, Ti-powder was loaded into the Ti-felt GDL in URFCs to produce an effective pore distribution for water management in the membrane. Then, the effect of this Ti-powder loading on the cell performance was examined for both fuel cell and electrolysis operations. Experimental results revealed that the Ti-powder loading significantly improved the fuel cell performance under fully humidified conditions (relative humidity (RH) = 100%), but not under relatively dry conditions (RH = 66%). In contrast, the Ti-powder loading had no effect on the electrolysis performance. © 2011 Elsevier B.V. All rights reserved.


Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | Nakano A.,Japan National Institute of Advanced Industrial Science and Technology | Hasegawa Y.,Japan National Institute of Advanced Industrial Science and Technology | And 6 more authors.
International Journal of Hydrogen Energy | Year: 2010

The flow characteristics of circulating water in a proton exchange membrane (PEM) electrolyzer were experimentally evaluated using a small cell and two-phase flow theory. Results revealed that when a two-phase flow of circulating water at the anode is either slug or annular, then mass transport of the water for the anode reaction is degraded, and that the concentration overvoltage increases at higher current density compared to that when the flow is bubbly. In a serpentine-dual flow field, when both phases of the two-phase flow are assumed laminar, then the increase in pressure drop caused by the increase in gas production can be explained relatively well using the Lockhart-Martinelli method with the Chisholm parameter. The optimal flow rate of circulating water was also discussed based on mass balance analysis. © 2010 Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu.


Hwang C.M.,University of Tsukuba | Ishida M.,University of Tsukuba | Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | And 6 more authors.
International Journal of Hydrogen Energy | Year: 2011

Polymer electrolyte-based unitized reversible fuel cells (URFCs) combine the functionality of a fuel cell and an electrolyzer in a single device. In a URFC, titanium (Ti)-felt is used as a gas diffusion layer (GDL) of the oxygen electrode, whereas typical carbon paper is used as a GDL of the hydrogen electrode. Different samples of Ti-felt with different structural properties (porosity and fiber diameter) and PTFE content were prepared for use as GDLs of the oxygen electrode, and the relation between the properties of the GDL and the fuel cell performance was examined for both fuel cell and electrolysis operation modes. Experimental results showed that the cell with a Ti-felt GDL of 80 μm fiber diameter had the highest round-trip efficiency due to excellent fuel cell operation under relatively high-humidity conditions despite degradation in performance in the electrolysis mode. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Ito H.,Japan National Institute of Advanced Industrial Science and Technology | Maeda T.,Japan National Institute of Advanced Industrial Science and Technology | Kato A.,Takasago Thermal Engineering Co. | Yoshida T.,Daiki Ataka Engineering Co. | Ulleberg O.,Institute for Energy Technology of Norway
Journal of the Electrochemical Society | Year: 2010

Unitized reversible fuel cells (URFCs) combine the functionality of a fuel cell (FC) and of an electrolyzer (Ely) in a single device. In polymer electrolyte URFCs, gas purging is crucial in switching from the Ely to the FC operation. A gas purge model was developed here to clarify the relationship between the purge time and the gas flow rate. The model considers evaporation and diffusion of liquid water in the gas diffusion layer and membrane. To validate our model, we compared model predictions of high frequency resistance vs purge time with experimental results for two URFCs of different sizes at different purge flow rates. The simulated curves agree well with the experimental curves. © 2010 The Electrochemical Society.


Takano H.,Daiki Ataka Engineering Co. | Izumiya K.,Daiki Ataka Engineering Co. | Kumagai N.,Daiki Ataka Engineering Co. | Hashimoto K.,Tohoku Institute of Technology
Applied Surface Science | Year: 2011

The active catalysts for methane formation from the gas mixture of CO 2 + 4H 2 with almost 100% methane selectivity were prepared by reduction of the oxide mixture of NiO and ZrO 2 prepared by calcination of aqueous ZrO 2 sol with Sm(NO 3) 3 and Ni(NO 3) 2. The 50 at%Ni-50 at%(Zr-Sm oxide) catalyst consisting of 50 at%Ni-50 at%(Zr + Sm) with Zr/Sm = 5 calcined at 650 or 800 °C showed the highest activity for methanation. The active catalysts were Ni supported on tetragonal ZrO 2, and the activity for methanation increased by an increase in inclusion of Sm 3+ ions substituting Zr 4+ ions in the tetragonal ZrO 2 lattice as a result of an increase in calcination temperature. However, the increase in calcination temperature decreased BET surface area, metal dispersion and hydrogen uptake due to grain growth. Thus, the optimum calcination temperature existed. © 2011 Elsevier B.V. All rights reserved.


Kato Z.,Tohoku Institute of Technology | Bhattarai J.,Tribhuvan University | Kumagai N.,Daiki Ataka Engineering Co. | Izumiya K.,Daiki Ataka Engineering Co. | Hashimoto K.,Tohoku Institute of Technology
Applied Surface Science | Year: 2011

For the anode composed of electrocatalyst oxide, intermediate layer and titanium substrate, the substitution of a certain amount of iridium with tin in the IrO 2 intermediate layer was remarkably effective in elongating the life of the anode in preventing oxidation of the substrate titanium during oxygen evolution. The longest life was realized by preparation of intermediate layer with uniform thickness by brush-coating of H 2IrCl 6-SnCl 4 butanol solution and subsequent calcination. The anode with the intermediate layer prepared from 0.04 M H 2IrCl 6-0.06 M SnCl 4 butanol solution showed the best performance, that is, the oxygen evolution efficiency higher than 99.8% for more than 4300 h in the electrolysis of 0.5 M NaCl solution of pH 1 at the current density of 1000 Am -2. An increase in SnCl 4 concentration decreased the viscosity of the coating solution with a consequent enhancement of uniformity of the intermediate layer but decreased the thickness of the intermediate layer acting as a barrier to prevent oxidation of titanium. Thus, the best performance was attained at an intermediate SnCl 4 concentration. The growth of an oxide layer on titanium during electrolysis occurred and was found by the potential increase. © 2011 Elsevier B.V. All rights reserved.


El-Moneim A.A.,Alexandria University | Bhattarai J.,Tribhuvan University | Kato Z.,Tohoku Institute of Technology | Izumiya K.,Daiki Ataka Engineering Co. | And 2 more authors.
ECS Transactions | Year: 2010

For hydrogen production by seawater electrolysis the anodic reaction should be oxygen evolution without forming chlorine. The durability of anode was significantly extended by determining factors influencing the lifetime in preparation of the electrocatalysts and by improving the intermediate layer preventing oxidation of the titanium substrate in the anode. The electrocatalysts for durable anode should not be too thin and too thick. The specific resistance of deposit affected the thickness of electrocatalysts deposited anodically. Mo 6+ increases the specific resistance while W 6+ and Sn 4+ decrease it. The best composition of the electrolyte for preparation of Mn 1-x-yMo xSn yO 2+x electrocatalyst was determined on the basis of the roles of additive elements. The lifetime was significantly extended by repetitive deposition for 30 min three times with washing and drying of the anode and renewing of the electrolyte at every intermission. The intermediate layer consisting of Sn 1-x-yIr xSb yO 2+0.5X instead of IrO 2 prevented effectively oxidation of titanium. ©The Electrochemical Society.

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