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11Статья поступила в редакцию 12.08.2010. Ред. рег. № 854
The article has entered in publishing office 12.08.2010. Ed. reg. No. 854
FUNDAMENTAL APPROACHES TO FUEL CELL TECHNOLOGY
S. Sugawara, A. Ohma, Y. Tabuchi and K. Shinohara
Nissan Research Center NISSAN Motor Co., Ltd.
1, Natsushima-cho, Yokosuka, Kanagawa 237-8523, Japan Author for correspondence, Dr. K. Shinohara
Nissan Research Center Nissan Motor Co., Ltd.
1, Natsushima-cho, Yokosuka, Kanagawa 237-8523, Japan Telephone: +81-46-867-5331, Fax: +81-46-866-5336, E-mail k-shino@mail.nissan.co.jp
The biggest issue that must be addressed in promoting widespread use of fuel cell vehicles (FCVs) is to reduce the cost of the fuel cell system while maintaining and improving its performance and functionality. Specifically, the overall system must be simplified and the cost of the fuel cell stack itself must be reduced. The technological challenge here is to secure the necessary transport properties and electrochemical reactions in the fuel cell stack so as to ensure high cell voltage under wide-ranging conditions for temperature, humidity, oxygen concentration, reactant gas flow rates and current densities. Toward that end, the effects of these parameters on fuel cell performance must be understood more thoroughly in order to identify and control the main governing factors involved. We have been working to elucidate transport and reaction phenomena by applying experimental analyses and computational science methods in a complementary manner to investigate the phenomena that occur in a fuel cell. This article presents an overall picture of these analyses.
ФУНДАМЕНТАЛЬНЫЕ ПОДХОДЫ К ТЕХНОЛОГИИ ТОПЛИВНЫХ ЭЛЕМЕНТОВ
С. Сугавара, А. Ома, Й. Табучи, К. Шинохара
Самая серьезная задача, которую необходимо решить для обеспечения более широкого использования автомобилей на топливных элементах - это снижение стоимости системы на топливных элементах с одновременным сохранением и улучшением ее эксплуатационных характеристик и функциональности. В частности, необходимо упростить систему в целом и снизить стоимость самой батареи топливных элементов. Технологическая сложность здесь состоит в обеспечении необходимых транспортных свойств и электрохимических реакций в батарее топливных элементов для получения высокого напряжения элемента в широком диапазоне температур, уровней влажности, концентраций кислорода, расходов взаимодействующих газов и плотностей тока. Это требует более глубокого понимания влияния этих параметров для определения и управления основными определяющими факторами. Мы занимаемся изучением процессов переноса и взаимодействия, происходящих в топливном элементе, путем проведения взаимодополняющих экспериментальных исследований и расчетов. В данной статье приведена общая картина этих исследований.
Kazuhiko Shinohara
Organization(s): Senior Manager, Advanced Materials Laboratory, Nissan Research Center, Nissan Motor Co., Ltd. , Ph.D in Materials Science.
Education: Tokyo Inst. Technology (1975-1981, 1984-1986, 1991-92).
Experience: Research Scientist, Stanford University (1988-1990). Deputy Director, Technology Research Association FC-Cubic (2010).
Main range of scientific interests: Materials Science, Energy Conversion Devices, Materials Analysis, Fuel Cell Fundamental Analysis.
Organization(s): Advanced Materials Laboratory, Nissan Research Center, Nissan Motor Co., Ltd., Manager, Dr. Eng.
Education: Waseda University, School of Science and Engineering (1988-1992), Japan Advanced Institute of Science and Technology, School of Materials Science (1993-1995), Yokohama National University, Graduate School of Engineering (2006-2009).
Experience: Asahi Glass Co., Ltd., Engineer (1995-1998), Atotech Japan K.K., Engineer (19982002), Atotech USA Inc., Chemist (1999-2002).
Main range of scientific interests: Electrocatalysis, electrochemical measurement, energy conversion, corrosion inhibition, nanoparticles, electrodeposition, crystallization.
Seiho Sugawara
il
ifl
Atsushi Ohma
Organization(s): Advanced Materials Laboratory, Nissan Research Center, Nissan Motor Co., Ltd., Manager, Dr. Eng.
Education: Waseda University (1991-1995), Tokyo Inst. Technology (2007-2010).
Experience: Toshiba Co., Ltd., Engineer (1995-2002), Toshiba International Fuel Cells Co., Ltd., Engineer (2002).
Main range of scientific interests: Energy Conversion, Mechanical Engineering, Thermal Dynamics, Electrochemistry, Computational Science, Fuel Cell Fundamental Analysis.
Yuuichiro Tabuchi
Organization(s): EV System Laboratory, Nissan Research Center, Nissan Motor Co., Ltd., assistant manager.
Education: .University of Tokyo, aerospace engineering (1995-1999).
Experience: NGK cooperation (1999-2004), Research Scientist, The Pennsylvania State University (20062007).
Main range of scientific interests: Energy Conversion Devices, Mechanical Engineering, Fluid Dynamics, Fuel Cell Fundamental Analysis
1 Introduction
A stationary fuel cell system called ENE-FARM is already being sold in Japan for home use as one type of solid polymer electrolyte fuel cell (PEFC). It is projected that commercialization of fuel cell vehicles (FCVs) will begin in 2015 and that the FCV business will become profitable from around 2025, as shown in Fig. 1. This scenario envisioned for the commercialization of FCVs has been proposed by the Fuel Cell Commercialization Conference of Japan (FCCJ). In line with this scenario, manufacturers and other organizations are moving ahead with vigorous research and development efforts. However, in order to promote widespread use of FCVs by the general public, the vehicles will need to have
suitable cost and performance levels to be accepted by consumers in the initial stage of commercialization. To usher in full-scale commercialization, it will be necessary to demonstrate that FCVs have the required technologies to be competitive with conventional vehicles in terms of cost and performance.
Issues pointed out in the FCVs offered to date include power density, subzero startup capability, durability and cost, among others. With the exception of cost, extensive research and development efforts have produced technologies for addressing these issues, with the result that current FCVs now compare favorably with conventional vehicles fitted with an internal combustion engine (ICE). However, there remains a need to reduce the cost of FCVs substantially.
Commercialization Scenario for FCVs and H2 Stations
CD &
B
£ Ö o
"Ü
00
Phase 1 Technology Demonstration Phase 2 j Technology & Market ! Demonstration |
[JHFC-21 2010 2011 [Post JHFC] 2015 j;
Phase 3 Early Commercialization
2025
•Solving technical issues and promotion of review regulations (Verifying & reviewing development progress as needed)
•Verifying utility of FCVs and H2 stations from socio-economic viewpoint
Approx. 2 million FCVs
•Expanding production and sales of FCVs while maintaining convenience of FCV users
•Reducing costs for H2 stations and hydrogen fuel
•Continuously conducting technology development and review of regulations
Phase 4 Full Commercialization
[Profitable business
2026
ation Period 1
Contribute to diversity of energy sources and reduction of CO2 emissions
Increase numbers'of FCV and H2 stations^ based on profttâbfe business
_
Costs for H2 station construction and hydrogen reach targets, making the station business viable. (FCV 2,000 units/station)
Period in which preceded H2 station building is necessary
Increase of FCV numbers through introduction of more vehicle models
I
Note: Vertical axis indicates the relative scale between vehicle number & station number.
Year
Precondition: Benefit for FCV users (price/convenience etc.) are secured, and FCVs are widely and smoothly deployed
Fig. 1. Commercialization scenario proposed by FCCJ
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
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Reducing the cost of FCVs requires not only a reduction of the cost of the fuel cell stack itself, but also a substantial reduction of the cost of the overall fuel cell system. Naturally, the effect of volume production can be expected to bring down the cost at the time of full-scale commercialization. Additionally, in terms of technology, it will be necessary to develop a fuel cell stack capable of delivering the necessary and sufficient performance even in systems simplified for cost savings.
One effective measure for achieving a low-cost fuel cell system is to simplify its complex structure, including that of the cooling system and the various systems for supplying reactant gases, water, and oxygen. However, the challenge of maintaining and improving the performance and durability of the fuel cell system while simplifying its constituent parts will be one of the biggest issues that will have to be addressed in future research and development work. For example, the structure of the catalyst layer of a fuel cell consists mainly of platinum (Pt), carbon, electrolyte and pores. Measuring this structure and composition accurately is still difficult to accomplish. Nor is it easy to measure accurately the electrochemical behavior of the Pt catalyst under various cell operating environments or the states and mobility of water, oxygen, protons and other substances involved in the internal electrochemical reactions. Moreover, the structure and functionality of the electrolyte membrane, gas diffusion layer, separator plates and other components making up a fuel cell influence changes in the internal environment of the catalyst layer, making it even more difficult to measure the resultant phenomena.
In order to understand the complex phenomena occurring inside a fuel cell and define their governing factors, we have been developing experimental techniques at Nissan for measuring the properties of each of the constituent materials along with methods for modeling their structures. In parallel with those efforts, we have used computational science techniques in an attempt to explicate phenomena that occur simultaneously and in parallel from the macroscale to the microscale level.
As techniques for analyzing the structures and states of materials, we use structural visualization methods such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as neutron radiography and X-ray computed tomography to gain an understanding of structures from the mesoscale to the microscale level. Moreover, we also apply Raman spectroscopy and other visualization techniques to analyze the distribution and concentration of water. Examples of the application of these techniques will be described later. Simulations using phenomenological models based on continuum calculations are also run in parallel to gain a better understanding of the different types of polarization that occur in a fuel cell.
Analyses conducted at the microscale to the mesoscale level are aimed at explicating the factors inhibiting catalytic reactions. The objectives here are to
ascertain the factors affecting reactants and their respective degree of influence on cell performance and to identify the governing factors involved. In the case of electrode reactions, we have developed fundamental materials that model the structures and phenomena involved as well as experimental methods of using such materials in order to identify the elementary reaction steps. We have also developed structures for modeling transport phenomena at the catalyst layer in order to analyze the mobility of protons, oxygen and water that are transported here. Computational science methods such as first-principle computations and molecular dynamic computations are also effective tools in analyses that probe as far as the microscale level. These methods are also being used as analytical tools.
In the process of applying cost reduction technologies based on such phenomenological analyses, still other new issues arise. One example that can be cited is catalyst durability. It has been found that the principal causes of performance degradation in a fuel cell are Pt catalyst dissolution, precipitation and aggregation, oxidation of the carbon support of the Pt catalyst, and decomposition of the electrolyte membrane. Detailed phenomenological analyses have revealed that the governing factors of these degradation phenomena are related to the structure and properties of the materials themselves. Other governing factors include the electric potential applied to the catalyst and associated potential cycling as well as operational and environmental conditions such as humidity and temperature. Based on this technical knowledge, we have substantially improved the durability of the fuel cell stack by effectively controlling these operational and environmental conditions. However, it is predicted that other new degradation modes may occur in the future as a result of using of new types of catalysts, such as core-shell catalysts, or new non-platinum catalyst materials in order to reduce the Pt loading or due to the use of a hydrocarbon material for the electrolyte membrane.
In order to popularize FCVs in the coming years, new materials must be developed that anticipate the occurrence of such durability issues. For that reason, at Nissan we are also developing methods of assessing the durability of new materials intended for fuel cell application.
This article describes the techniques we have developed so far at Nissan for analyzing the phenomena occurring inside a fuel cell and identifying their governing factors. It also describes the activities under way to develop new materials for future fuel cells.
2. Fuel Cell Analysis
2.1 Research for Macro-scale phenomena Operating a fuel cell at higher current densities, thus allowing a lower level of Pt loading, is one way of reducing the cost of PEFCs for vehicle application. However, in addition to activation overpotential that
occurs during high current density operation, there are also other issues that must be addressed. These include an increase in concentration overpotential caused by lower oxygen partial pressure at the reaction sites and suppression of the inhibition of proton transfer (ohmic loss) due to a higher electrolyte membrane temperature resulting from heat generation accompanying the electrochemical reactions.
We have used a neutron radiography to visualize the liquid water distribution in the flow channels and a segmented cell to analyze the effects on polarization of the current density distribution along the flow channels. The results obtained have made clear the influence of the flow channel geometry on concentration overvoltage and ohmic loss [1-5]. However, in order to operate fuel cells at even high current densities for the purpose of reducing the system cost, further progress in material design techniques will be essential, in addition to analyzing how the reaction distribution and material composition in the flow channels affects polarization. It is necessary to understand how polarization is affected by the material composition and reaction distribution under the ribs and channels and in the thickness direction of the membrane electrode assembly (MEA). The constituent materials need to be designed so as to minimize the effects of such factors.
Fig. 2. Polarization curves with different rib/channel widths and membrane thicknesses
distribution under the ribs and channels area and between the anode and cathode, something that was difficult to do previously [6]. During high current density operation (especially at 1.5 A/cm2 or higher), it is known that a large liquid water distribution forms inside the GDL under the ribs and channels and that I-V (current-voltage) characteristics varies greatly depending on the rib/channel geometry (Figs. 2 and 3).
The results of a numerical analysis (solid lines in Fig. 2) and temperature measurements (Fig. 4) obtained with micro-thermal couples inserted between the anode catalyst layer and the micro-porous layer have revealed that the liquid water distribution originates by a temperature distribution under the ribs and channels. The results have also shown that improving water transport between the electrodes such as by using a thinner electrolyte membrane and shortening the heat transfer distance by narrowing the rib and channel widths are effective in reducing concentration overvoltage and ohmic loss during high current density operation [7-8].
In future work, it will be important to understand how the material composition in the thickness direction of the MEA affects polarization as well as the effects of the non-steady-state vehicle operating environment on conditions (water, temperature and reaction distributions) inside the MEA [9-11].
Compression pressure Cell voltage —c^2.0 MPa —0—1.0 MPa
1
08 I
0.7 Ü
0.5 g c
03 I
P
0.2
v o
Temperature rise (between Anode MPL- CL)
0.5 1 1.5 2 Current density A/cm2
2.5
Fig. 3. Liquid water distribution at 2.5 A/cm
The use of a neutron radiography has improved the spatial resolution of visualization techniques in recent years, making it possible to visualize the liquid water
Fig. 4. Temperature increase at the interface between microporous layer and catalyst layer under different operating conditions
The foregoing analyses have shown the importance of understanding water and heat transport properties of the materials constructing the cell and MEA, and net water transport through the membrane in order to reduce polarization under high current densities. However, the
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
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transport properties of the electrolyte membrane, GDL and other constituents vary considerably because of their complicated microstructures and are still not well understood. That lack of understanding of these phenomena is an obstacle that prevents researchers from obtaining material design guidelines for improving the net water and heat transport properties through the membrane.
A large water concentration gradient between the electrodes is created during operation at a high current density. Accordingly, it is important to measure the water content distribution in the membrane in an environment that simulates the operating conditions. Previously, it was necessary to use a thick electrolyte membrane of several 100 ^m in thickness in such measurements because of the limitation of spatial resolution obtainable for water. In contrast to that situation, the use of Raman spectroscopy in recent years has made it possible to measure the water content distribution in the electrolyte membrane with a spatial resolution of several ^m. It is now becoming possible to obtain measurements using a membrane thickness that is actually employed in vehicle applications (Figs. 5 and 6) [12].
Fig. 5. Typical Raman spectra in the membrane thickness direction in the presence of water flux thorugh the membrane
Fig. 6. Water content distribution with different membrane thicknesses
In order to design the GDL for improving heat conductance, it is important to visualize and quantify the complex microstructures of the GDL. That has been
difficult to do so far because of the limited spatial resolution of the visualization methods available, including neutron radiography. In recent years, however, visualization of microstructures has become increasingly possible through the use of X-ray computed tomography (Fig. 7) [13].
Further improvement of water content measurement techniques and the spatial resolution of microstructure visualization methods will be an important task for future work. It will also be important to obtain a better understanding of how the material factors of the constituent elements of the MEA affect transport properties.
Fig. 7. Microstructure of carbon paper GDL (TGP-H-120) obtained by X-ray CT technique
2.2 Mesoscale phenomena
Full-scale penetration of FCVs will require a reduction of the Pt loading used for the MEA catalyst layer to the level of the amount of precious metals currently used in the exhaust gas treatment system of conventional ICE vehicles. To accomplish that, it will be necessary to make more effective use of the platinum contained in the catalyst layer. Naturally, increasing the active surface area of the platinum contributing to the electrochemical reactions is important in using platinum more effectively. It is also essential to design the fuel cell so as to maintain a higher concentration of reactants transported to the Pt surface and to ensure a homogeneous reaction distribution as much as possible within the catalyst layer. Such measures can achieve high I-V characteristics with a lower Pt loading. Accordingly, in order to promote more effective use of platinum, it is necessary to understand the effects on the reaction distribution and voltage loss (polarization) that occur in the catalyst layer. Other issues involved here include ascertaining the transport properties and the enabling microstructures at the mesoscale and microscale levels, as they determine the reaction distribution.
The catalyst layer generally has a random porous structure that is less than 10 ^m thick and consists of platinum, carbon, ionomer and pores (Fig. 8). Platinum particles are distributed not only on the outer surface of the carbon support but also inside it, and the area around
the carbon agglomerate is covered with the ionomer. Trying to visualize and clarify this microscopic structure was previously a challenge technologically, but it has gradually been explicated in recent years as a result of the progress seen in analytical techniques and devices, including three-dimensional transmission electron microscopy tomography (3D-TEM) and scanning transmission electron microscopy (STEM) [14-15]. Moreover, analytical techniques have also been developed that use electrochemical atomic force microscopy (e-AFM) to ascertain the proton transfer regions on the electrolyte membrane surface microscopically [16]. This technique is also expected to be applied to the ionomer inside the catalyst layer in the future.
At Nissan, we have applied both experimental analysis and computational science methods to investigate the structure of the ionomer covering the catalyst. In a study based on molecular dynamics (MD), we examined the structure of a model electrode consisting of the electrolyte (Nafion® ionomer) covering the graphite surface and water adsorbed on the surrounding area [17].
Electrolyte membrane
Anode Anode
GDL Catalyst
Layer
- 1 Sffïfîfij
■ . ■ 10 um <->
Fig. 8. Cross-sectional images of a membrane electrode assembly (MEA) and the catalyst layer
Ionomer
Water
5.6 nm
Carbon
Fig. 9. Final snapshots of the Nafion® morphology of 12 oligomers in the vicinity of the bare graphite sheet at A=22. Backbones (gray beads), side chains (green beads), sulfonic acid groups (red/yellow beads), water (orange beads), hydronium ions (white/red beads) are visualized
It was observed that the Nafion® ionomer tended to be adsorbed on the graphite surface centered on the main chain backbone of hydrophobic fluorocarbons while the side chains of hydrophilic sulfonic acid tended to be oriented on the opposite side of the graphite surface. Water was also selectively adsorbed around the side chains, and a two-dimensional water cluster structure formed on the Nafion® ionomer surface (Fig. 9). The adsorption structure of the Nafion® ionomer was
influenced by the condition of the graphite surface. One noteworthy result is that the side chains were oriented toward the side with the graphite surface owing to the presence of surface functional groups such as carboxylate groups (COO-), which suggested the possibility that the structure of the adsorbed water may have changed as a result.
As an example of an experimental analysis, small angle neutron scattering (SANS) was applied to investigate the structure of water clusters formed in the interior and on the surface of the ionomer in the catalyst layer [18]. As a result, it was found that the size of the water clusters varied depending on the type of carbon support used (Ketjenblack (KB) or graphitized Ketjenblack (GKB)) and whether platinum was present or not. These results agreed qualitatively with the findings of the MD simulation mentioned above. An analysis was made of the electric double-layer capacitance using a model catalyst layer (pseudo catalyst layer) fabricated of a carbon support and ionomer and without any platinum. It was found that the coverage ratio and mean thickness of the ionomer covering the carbon support could be calculated [19, 20]. The results revealed that the coverage ratio of the ionomer differed depending on the type of carbon support used. With the KB system having many pores in the interior, approximately 30% of the entire surface was covered, whereas nearly 100% of the surface was covered with the GKB system with virtually no interior pores (Fig. 10). When the weight ratio of the ionomer to the carbon support (I/C weight ratio) was set at 0.9, the mean thickness of the ionomer was around 2-3 nm [19]. Even when the I/C weight ratio was varied over a wider range of 0.4 to 1.8, the coverage ratio remained nearly constant and only the mean thickness of the ionomer changed [7].
Fig. 10. RH dependence of double-layer capacitance of pseudo
catalyst layers (PCLs) with different carbon supports. Circles and squares denote KB and GKB systems, respectively
As described here, transport properties are one factor that is directly related to the microstructure of the catalyst layer. Phenomena occurring within the catalyst layer with its complex microporous structure can be understood by making clear how its effective properties relate to the microstructure. Toward that end, we have
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
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developed techniques at Nissan for measuring the effective transport properties of oxygen, protons, water and other substances that are related to the reactions occurring at the catalyst layer. These techniques have been used to analyze transport phenomena in relation to various structural factors [19-24].
With regard to oxygen transport, we have devised a method for calculating analytically oxygen transport resistance within the catalyst layer based on measurements of the limitting current density using diluted oxygen [21]. This technique was used to examine the effect on oxygen transport when the Pt loading was reduced [22]. The results confirmed that oxygen transport resistance increased markedly in the catalyst layer accompanying a reduction of the Pt loading even though the catalyst layer became thinner (Fig. 11). Taking that result into account, we constructed a model that explains the measured oxygen transport resistance as a combined resistance value consisting of Knudsen diffusion resistance in the pores along the thickness direction of the catalyst layer and the transport resistance of oxygen passing through the interior of the ionomer toward the Pt surface. This model suggests the possibility that the effects of oxygen transport resistance through the catalyst layer may become more pronounced owing to the reduction of the effective Pt surface area when the Pt loading is reduced.
GKB support system showed higher ce values (Fig. 12). The reason for this result was examined in separate analyses of the structural factors (volume fraction and tortuosity) and proton conductivity (c) intrinsic to the ionomer. In the case of the pseudo catalyst layers with the GKB support system, it was found that the proton conductivity (c) of the ionomer covering the GKB support was equal to the value measured for the electrolyte membrane alone (cmem). However, in the case of the KB support system, it was observed that the value might be smaller than c mem. One reason for that can be understood as follows. Because functional groups are present on the KB support surface, the water content of the ionomer covering the KB support may be lower than that of the ionomer covering the GKB surface under a condition of equal humidification. The same observation was made in an analysis of the change in the measured ceff values when the I/C weight ratio was increased for pseudo catalyst layers with the KB support system. The results showed that the c value of the ionomer covering the KB support tended to approach cmem as the IC weight ratio was increased [20]. These tendencies were consistent with the results of the above-mentioned structural analysis in which the structure of the adsorbed water differed depending on the type of carbon support used and whether or not functional groups were present on the surface.
Fig. 11. Reactant gas transport resistance (Rother) in CLs as a function of Pt loading. Results for oxygen and hydrogen are shown in black and gray, respectively
Because proton transport resistance within the catalyst layer is a complex phenomenon ascribable to the ionomer-covered structure, it has been investigated using pseudo catalyst layers like those describe above. A method was devised for measuring the effective proton conductivity (ceff) in pseudo catalyst layers using a hydrogen pump technique. The MEA fabricated for this measurement had a compound structure in which the pseudo catalyst layers were sandwiched between two electrolyte membranes. This method was used to measure ceif of pseudo catalyst layers with either KB or GKB carbon supports. The results revealed that the pseudo catalyst layers with the
Fig. 12. Comparison of effective proton conductivity (aeff) of PCLs with different carbon supports. Circles and squares denote KB and GKB systems, respectively
For investigating water transport in the catalyst layer, we first developed a method of measuring transport resistance [23]. Specifically, we fabricated several types of MEA having different catalyst layer thicknesses. A different level of water vapor activity was provided on each side of the MEA, and the water flux was measured in the direction of the catalyst layer thickness. Water transport resistance was calculated by dividing the difference in water vapor activity by the measured water flux. The results were then plotted in relation to the thickness of the catalyst layer, and water transport resistance within the catalyst layer was estimated from the change in the plotted values. As a result, it was found that water transport resistance correlated linearly with the catalyst layer thickness (Fig. 13).
Fig. 13. Water transport resistance of MEA as a function of total CL thickness. Squares, triangles, and circles indicate measured
values at 60, 70, 80 deg. C, respectively. Plots at total CL thickness zero correspond to measured values with membrane
We also devised a model for expressing the estimated water transport resistance as a combined resistance value consisting of Knudsen diffusion resistance of the water vapor in the catalyst layer pores, the liquid water transport resistance of the ionomer interior and surface and the gas-liquid phase change resistance involving both types. This model was used to investigate the contribution of each type of resistance to the total. The results indicated that the above-mentioned linearity coincided with the result for the interpolated intercept and the membrane alone, implying that the gas-liquid phase change resistance was at a negligible level compared with the other two values (Fig. 14).
RO2 macro (in Pores)
q_ ionomer " "
Membrane
CCL
GDL
proton
the analysis of the water structure. With the GKB system, larger water clusters developed inside the ionomer and on the surface, and the resultant improvement of connectivity presumably worked to improve water transport properties.
Based on the analysis results presented here concerning the microstructure of the catalyst layer, transport properties and transport resistance, we devised a model for predicting the reaction distribution in the catalyst layer interior and the I-V characteristics [25, 26]. A schematic of the model is shown in Fig. 14. In order to predict the reaction distribution in the thickness direction of the catalyst layer during steady-state operation, oxygen transport resistance and proton transport resistance are measured separately as explained above, and the measured values are applied to the model as the input conditions. One major feature of this model is that it takes into account the transport resistance (RO2_micro) of oxygen passing through the ionomer inside the catalyst layer, reflecting the measured oxygen transport resistance result. Another feature is that the model takes into account the fact that RO2_micro is inversely proportional to the effective Pt surface area per unit area of the catalyst layer and that the effective Pt surface area varies according to the coverage ratio of Pt oxides [27]. This model does not reflect the aforementioned results for water transport resistance or the effects of product water.
Fig. 14. Steady-state 1-dimensional model of a cathode caltalyst layer
Furthermore, the water vapor transport resistance through the pores was smaller than the liquid water transport resistance of the ionomer interior and surface, revealing the possibility that it governs water transport in the direction of the catalyst layer thickness [23]. Water transport resistance in the catalyst layer is also influenced by the type of carbon support used for the catalyst. When the catalyst layer was supported by the GKB system, a tendency was observed for the influence of the liquid water transport resistance of the ionomer interior and surface to become more pronounced, compared with the results seen for the KB catalyst support system [24]. The reason for that can be understood in relation to the results mentioned earlier for
Current density / A cm"'
Fig. 15. Comparison of I-V characteristics for different cathode Pt loadings. Measurement conditions: 80 deg. C, ambient pressure, H2/air gas streams, 100/100% RH
Fig. 15 compares the iR-free I-V characteristics measured for two types of MEAs with different cathode Pt loadings (data plots) and the I-V characteristics predicted with the model (solid lines). The measurement conditions were atmospheric pressure, 100% RH and H2/air gas streams. The measured results for the lower Pt loading show a tendency for the cell voltage to decline under both low and high current densities. In addition to the former decline, attributable to a reduction of the Pt effective surface area (kinetics), the model also captured the latter tendency ascribable to an increase in the transport resistance of oxygen passing through the ionomer.
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
© Scientific Technical Centre «TATA», 2010
Fig. 16 presents a breakdown of the voltage loss for the measured I-V characteristics in Fig. 14 at 1.0 Acm-2. The results indicate that the voltage loss (n proton) ascribable to proton transport resistance decreased because of the thinner catalyst layer resulting from the reduced cathode Pt loading. However, the voltage loss (no2_micro) attributable to the transport resistance of oxygen passing through the ionomer increased.
0.52 0.50 > 0.48
2 0.46 <
o 0.44
0.40 0.38
Fig. 16. Voltage loss breakdown of measured I-V characteristics shown in Fig. 14 at 1.0 Acm-2
One of the first issues that needs to be tackled in future analyses of the catalyst layer is to explain the drop in I-V characteristics that occurs during operation under reduced humidification, which is one approach to reducing the cost of fuel cell systems. That will involve ascertaining the transport properties (oxygen, protons and water) related to the ionomer inside the catalyst layer under low humidification conditions as well as taking into account the effects of product water. In order to accomplish that, it will be necessary to examine in detail the microstructures related to each transport property inside the ionomer, based on the application of more microscopic design techniques and theoretical analyses. A key issue here will be to identify the governing factors for improving transport properties. It will also be necessary to investigate how the catalyst, ionomer and other materials and their manufacturing conditions affect the microstructures of the catalyst layer that is obtained. The principal controlling factors must be ascertained by using an experimental database of the manufacturing conditions and constructing logical explanations. Moreover, it will also be necessary to undertake further analyses of the electrochemical reactions. Because the platinum of the catalyst layer is covered by the ionomer, the effects of the ionomer on the electrochemical reactions occurring on the Pt surface in particular need to be investigated. As mentioned in references [28] and [29], computational science techniques and experimental methods using model electrodes should be applied to investigate these effects in greater detail.
Studies based both on theories of mesoscale phenomena and experimentation should be undertaken to optimize the catalyst layer structure so as to obtain higher I-V characteristics with reducing of platinum loading. That can be expected to lead to still more effective use of platinum in future systems.
2.3 Microscalephenomena
Because expensive platinum is used as the catalyst in PEFCs for vehicle application, the catalyst loading must be reduced in order to lower the fuel cell system cost. However, since the performance of an automotive fuel cell stack cannot be sacrificed for the sake of reducing the cost, catalyst activity must be substantially improved. Catalyst activity here means mass specific activity, i.e., the activity level per unit mass of platinum. The target value is around ten times the activity level of conventional Pt catalysts.
Ways of improving mass specific activity fall into two broad categories, improvement of the specific surface area of the catalyst and improvement of area specific activity. One approach to improving the specific surface area is to reduce the size of Pt nanoparticles. However, the diameter of the Pt nanoparticles now widely used for carbon-supported Pt catalysts is already as small as 2-3 nm. Reducing the size of nanoparticles further would cause durability to decline. Specific surface area can also be improved by positioning platinum only on the surface layer and substituting some other material for the particle core, as is done in the case of core-shell catalysts. However, even if the surface layer is thinned to a single atomic layer, the specific surface area is only improved by around twofold compared with that for Pt/C nanoparticles of 2-3 nm in size. Therefore, improvement of area specific activity is needed in order to enhance catalyst activity dramatically. Vigorous activities have been under way to improve area specific activity by means of alloying or recently by using core-shell catalysts. However, practical core-shell catalysts that provide a sufficient level of activity still do not exist. One reason is that there are still many aspects of catalyst development which necessarily rely on trial-and-error. This is related to the insufficient understanding of the oxygen reduction reaction mechanism and the catalyst factors influencing it. But it does not mean that the area specific activity now obtainable is approaching its upper limit. In fact, Pt plate catalysts have approximately ten times the area specific activity of Pt nanoparticles, but they are not practicable.
At Nissan we have been proceeding with efforts to analyze the factors governing area specific activity with the aim of improving it dramatically. The area specific activity of Pt catalysts in relation to the oxygen reduction reaction can be expressed by the following equation [30]:
where ia denotes area specific activity, i0 the exchange current density, 0 the oxide coverage ratio on the Pt catalyst surface, p- and y- symmetry factors, n overvoltage, R the universal gas constant, T temperature and r the Temkin parameter.
During PEFC operation, the range of cathode potential nearly coincides with the range of potential in
0.35 0.12
Pt loading / mg cm-2
which oxidation and reduction of the Pt surface occur. For that reason, the Pt oxide coverage ratio is a crucial parameter. Making clear the relationship between the Pt oxide coverage ratio and area specific activity is a key issue in elucidating the factors governing the latter.
The Pt oxide coverage ratio can be estimated from the quantity of electricity needed for oxide formation or reduction, by obtaining the current-potential curve by voltammetry in an inert gas atmosphere. However, a measurement made in an inert gas atmosphere is done under different conditions from the measurement of oxygen reduction activity in an oxygen atmosphere. Naturally, measurements cannot be made under both conditions simultaneously. In order to make clear the relationship between the Pt oxide coverage ratio and area specific activity, both should be measured under the same conditions and preferably at the same time. Therefore, we have used a rotating ring-disk electrode (RRDE) to develop a method for measuring both of them simultaneously [31, 32].
1.0
0.5
0.0
< -0.5 S
^ -1.0 -1.5
-2.0 -2.5
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Ed / V vs. RHE
Fig. 17. Disk current (/D), ring current (/R), and disk ORR current (/d,orr) as a function of disk potential (ED). Disk: Pt/C on GC, Ring: Pt, Disk potential scan rate: 50 mV s-1, Ring potential:
0.4 V, O2 concentration: 100%, Rotation rate: 900 r min1
Fig. 17 shows typical measured results for a carbon-supported Pt catalyst. The disk current (ID) includes two components. One is the double layer capacitive current; the other is a pseudo-capacitive current due to hydrogen adsorption/desorption and oxidation/reduction of the Pt surface. In other words, the same components as those of the current obtained by voltammetry in a nitrogen atmosphere are superimposed on the oxygen reduction reaction (ORR) current. In the measurement, the ring potential is kept at 0.4 V, the level at which the ORR current is the rate-determining step of diffusion. The detected ring current (IR) varies according to the consumption of oxygen at the disk electrode, and the disk ORR current (ID,ORR) is determined on that basis.
Fig. 18 shows the oxygen concentration dependence of the sum (ID,c/pc) of the double layer capacitive current and the pseudo-capacitive current. ID,c/pc was found by subtracting ID,ORR from ID in Fig. 17. It is clear from the
results in Fig. 18 that the oxygen concentration influences Pt oxide formation and reduction. This suggests that previous measurements of the Pt oxide coverage ratio made in a nitrogen atmosphere do not necessarily indicate the coverage ratio as the oxygen reduction reaction proceeds. The use of those measured values could possibly lead to a misinterpretation of the relationship between the coverage ratio and ORR area specific activity.
0.10
0.05
o
g 0.00 -0.05 -0.10
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Ed/ V vs. RHE
Fig. 18. Sum of capacitive and pseudocapacitive current density
on the disk electrode for various O2 concentrations. Disk: Pt/C on GC, Ring: Pt, Disk potential scan rate: 50 mV s-1, Ring potential: 0.4 V, Rotation rate: 900 r min-1
0.15
2 0.10
§
s
s
J- 0.05
0.00
0.2 0.4 0.6 0.8 1.0 1.2
n PtO
Fig. 19. Correlation between ORR area specific activity at 0.9 V and Pt oxide coverage at 0.9 V. Triangles: 6PtO was measured
by conventional voltammetry under a deaerated condition. Circles: 6PtO was measured by the simultaneous method in the presence of O2
Fig. 19 compares the correlation between the Pt oxide coverage ratio and area specific activity as measured with conventional voltammetry and with our simultaneous measurement method described here. In both cases, measurements were made at a potential of 0.9 V. In order to vary the coverage ratio, the potential was held at 1.1 V before ORR activity was measured and the hold time was varied. An analysis of the relationship between the coverage ratio and catalyst activity found with the conventional method in a nitrogen atmosphere reveals that the catalyst becomes inactive at a coverage
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
© Scientific Technical Centre «TATA», 2010
ratio of approximately 0.7, which is greatly influenced by the second exponential term on the right-hand side of Eq. (1). However, the relationship found with our proposed method, in which the coverage ratio is measured in an oxygen atmosphere simultaneously with catalyst activity, shows that the catalyst becomes inactive at a coverage ratio of approximately 1.0 and that the influence of the second exponential term is small. In other words, this indicates that, although Pt oxides block Pt activity sites, they have little influence on the activity of Pt particles that are not covered. Because our proposed method can separate area specific activity between that related to the Pt coverage ratio as the oxygen reduction reaction proceeds and that of uncovered Pt sites, it is expected to be useful in advancing the elucidation of the factors governing catalyst activity.
2.4 Durability
Vehicles are used under a wide variety of operating conditions and environmental circumstances. Two major differences between the operating conditions of automotive and stationary fuel cell systems are the frequent startup/shutdown cycles and load fluctuation of the former systems. Additionally, the composition of the air taken into an automotive fuel cell as the oxidant differs depending on the driving environment, which is still another distinct characteristic of automotive fuel cells. These factors cause various types of degradation in fuel cells for automotive use.
In consideration of safety following the shutdown of an automotive fuel cell, the shutdown procedure must reduce the stack voltage to zero. The simplest way to accomplish that is to create an air ambient at both electrodes by replacing hydrogen at the anode with air. In this case, air at the anode must be replaced again with hydrogen at the next cell startup. In both of these operations, hydrogen and air coexist at the anode during the replacement interval, albeit only briefly. It is known that corrosion of the cathode carbon catalyst support occurs at this time. Corrosion is caused by a rise in potential to a level of 1.5 V or higher in the cathode opposite the part of the anode where air is present [33]. Carbon support corrosion induces agglomeration of the Pt particles on the support, thereby reducing the effective surface area of the catalyst.
The cathode potential varies in a range of approximately 0.6-1.0 V accompanying load fluctuations, and this condition also causes a loss of the effective surface area of the Pt catalyst. It is understood that this is caused by Pt dissolution due to its direct exposure to a high potential when the potential rises sharply in the interval before a protective oxide film forms on the Pt surface [34]. We have conducted detailed studies of the relationship between the potential waveform and the loss of the effective surface area of the catalyst. The results have confirmed that a gradual potential rise is effective in suppressing degradation [35].
A better understanding of the mechanisms causing such degradation phenomena has led to the implementation of various measures for inhibiting performance decay. As a result, the durability of automotive fuel cells has been improved to a level sufficient for practical use. However, the adoption of such measures has also been one factor pushing up the cost of fuel cell systems. There is a need to develop new materials with higher levels of durability so as to reduce the system cost. Toward that end, at Nissan we have been working on the development of methods for evaluating the durability of new materials designed for fuel cell use.
Fig. 20 (a) and (b) illustrate two potential control patterns that Nissan has proposed for use in evaluating carbon support corrosion resistance and Pt dissolution resistance.
и К й
s.
>
ti
n
e t
о рц
1 s 1 s 1.5 V
(a)
3O
¿ЛЛ.....A
П . „ 1.0 V 4__
Л 2 "e ' "
Open circuit
Time
(b)
H К й
s.
>
ti
n
e t
о рц
Open circuit 3 s 3 s
^10 V\ Aiut-b-
. _ 0.6 V
6 s/cycle
Time
Fig. 20. Potential manipulation patterns for evaluation of (a) support corrosion resistance and (b) Pt dissolution resistance
These methods were proposed in a project to develop innovative technologies for reducing Pt usage, undertaken by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. The potential control patterns are used in common for evaluating a half cell and an MEA. Other common conditions used in an evaluation are listed in Table 1. In both cases, corrosion resistance and dissolution resistance are compared on the basis of the reduction of the electrochemically effective surface area (ECA) of the Pt catalyst.
The corrosion resistance of a standard catalyst (Pt/C) support and a support that was graphitized for improved corrosion resistance (Pt/Cgraphitized) was evaluated using a half-cell setup. The evaluation results are presented in Fig. 21. Platinum dissolution resistance was evaluated
for a standard catalyst (Pt/C) and a catalyst (Ptcoarse/C) whose Pt particles had been coarsened by a heat treatment process. The evaluation results obtained with a half-cell setup are shown in Fig. 22. The results confirmed the selective acceleration of the degradation phenomenon targeted for evaluation with each of the methods [36].
Table 1
Common evaluation conditions for both support corrosion resistance and Pt dissolution resistance
Accordingly, excellent resistance to poisoning by sulfur impurities is another key requirement of the catalyst.
0.6
>
2 a5
o <
<D
$ 0.4
"o
IS
o <D
0.3
d
0.2
0 0.1 0.2 0.3 0.4 0.5 0.6 Cumulative injection / ^mol cm-2
Fig. 23. Effect of various air contaminants on cell voltage at 1 A cm-2
Half-cell evaluation
Temperature 60 °C
Electrolyte Deaerated 0.1 M HClO4
MEA evaluation
Temperature 80 °C
Anode gas (RE/CE) Fully-humidified H2
Cathode gas (WE) Fully-humidified N2
NO (2 ppm)
SO2 (0.5 ppm)
80°C, 1 A/cm' H2/Air+Contaminants 50/50% RH 261/625 NmL/min.
80
s
"m 60
O
°o 40
<
w 20
10
100 1000 Cycle number / -
10000
Fig. 21. Decay in electrochemically effective surface area (ECA) by the evaluation protocol for support corrosion resistance
80
60
40
^ 20
O
w
100
1000 Cycle Number / -
10000
The effects of contamination by a low concentration of SO2 on I-V performance were investigated in more detail. The results revealed that sulfur species adsorbed on the Pt surface were oxidized into sulfuric acid ions at high potentials of 0.9 V or higher, with the result that the power generation capability was partially recovered. A potential level of 0.9 V is within the operating range of automotive fuel cells. It was also observed that the condensate water produced by power generation under a high humidification condition had the effect of recovering nearly the full power generation capability by removing sulfuric acid ions from the catalyst layer surface (Fig. 24). These results suggest that catalyst resistance to poisoning should be evaluated in terms of three characteristics: (1) ability to avoid sulfur adsorption at low potentials, (2) ability to oxidize at high potentials the sulfur species adsorbed at low potentials, and (3) ability to oxidize at high potentials SO2 contamination. We are now in the process of developing methods of evaluating these characteristics at Nissan.
0.00
Cumulative injection / ^mol cm-
0.05 0.10 0.15
0.7
m
c
0.6
Fig. 22. Decay in electrochemically effective surface area (ECA) by the evaluation protocol for Pt dissolution resistance
While fuel cell vehicles use oxygen in the air as the oxidant, the air also contains various impurities such as sulfur and nitrogen compounds. Such impurities can contaminate the cathode and poison the Pt catalyst, causing the I-V performance of the fuel cell to decline. Among the contaminants in the air, sulfur impurities in particular cause the fuel cell voltage to drop (Fig. 23) [37].
0.5
Recovery by high humidity operation
Recovery by N 1 0.639 i-V measurement \ 0.637 v_t
\ 0.600 \ A
80°C, 1 A/cm2
H2/Air+SO2
50/50% RH 261/625 NmL/min. 0.543
10
20 30 Time / h
40
50
Fig. 24. Trend of cell voltage at 1 A cm- during injection of 50 ppb SO2 to the cathode
0
0
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
© Scientific Technical Centre «TATA», 2010
3 List of Journal and Presentation
The research studies described here concerning fuel cell performance and analyzes of the phenomena involved are not limited to the research and development activities carried out at Nissan but also
include collaborative work done with outside research organizations. Related publications and conference presentations are listed in Table 2, 3 and 4. It is hoped that they will serve as useful references for a better understanding of the details of the explanations given here.
Table 2
List of publication
Authors Title Journals Macro Mass Transport Meso-Micro Mass Transport Dgradation Reaction
D. Kramer, E. Lehmann. P. Vontobel, A. Wokaun, G.G. Scherer, J. Zhang. R. Shimoi, K.Shinohara In situ neutron radiography investigation of the liquid water formation in hydrogen-fuelled polymer electrolyte fuel cells PSI Scientific Report 2003, March (2004; General Energy Volume V «
D. Kramer, J. Zhang 1, R. Shimoil. E. Lehmann, A. Wokaun, K. Shinoharal, G.G. Scherer In situ diagnostic of two-phase flow phenomena in polymer electrolyte fuel cells by neutron imaging Gordon Research Conference on Fuel Cells. Bristol Rl, USA, July 25-30. 2004. X
Y. Utaka and Y. Tasaki Effect of Surface Properties on Boiling Heat Transfer Characteristics in Micro-Channel Vapor Generator NIHON Kikaigakkai Ronbunshyu (B) . Vol.70, No.691. pp.737-743. 2004. X
Y. Utaka and Y. Tasaki Approach to Predicting Heat Transfer Characteristics of a Microchannel Vapor Generator NIHON Kikaigakkai Ronbunshyu , Vol.35. No.3, pp.123-128. 2004. X
D. Kramer, J. Zhang, R. Shimoi, E. Lehmann, A. Wokaun, K. Shinohara, G.G. Scherer In situ diagnostic of two-phase flow phenomena ir> polymer electrolyte fuel cells by neutron imaging Part A: Experimental, data treatment, and quantification Electrochimica Acta. 50, 2603-2614, 2005. «
X -G. Yang, N. Burke. C Y Wang, K. Tajiri and K. Shinohara "Simultaneous Measurements of Species and Current Distributions in a Polymer Electrolyte Fuel Cell under Low-Humidity Operation" Journal of Electrochemical Society, Vol. 152, DD. A759-A766, 2005. X
K. Yoshizawa, K. Ikezoe. K. Shinohara, D. Kramer. E. Lehmann, G. Scherer Analysis of Different Gas Diffusion Layer Materials in Fuel Cells Nihon Kikai Gakkai Nenji Taikai Koen Ronbunshu, 3, 277-278, 2005. X
Y. Utaka, Y. Tasaki and S. Okuda Behaviors of micro-layer in micro-channel boiling system applying laser extinction method NIHON Kikaigakkai Ronbunshyu (B) . Vol.71, No.704. pp.1133-1139 2005. «
A.Ohma, S.Suga, S.Yamamoto, K.Shinohara Phenomenon Analysis of PEFC for Automotive Use (i; Membrane Degradation Behavior During OCV Hold Test ECS Trans,. 3 (1), 519-529, 2006 X
S. Yamamoto and K. Shinohara Durability of Fuel Cell Stach for Automobile NISSAN Technical Report Vol. 59, 70.-74. 2006. X
J. Zhang, D. Kramer. R. Shimoi, E. Lehmann. A. Wokaun, K. Shinohara. G.G. Scherer In situ diagnostic of two-phase flow phenomena in polymer electrolyte fuel cells by neutron imaging. Part B: Material variations Electrochimica Acta 51, 2715-2727, 2006 «
A.Ohma. S.Suga, S.Yamamoto, K.Shinohara Membrane Degradation Behavior during Open-Circuit Voltage Hold Test J. Electrochem. Soc. 154. B757. 2007. X
Boillat, D. Kramer. B. C. Seyfang, G. Frei. E. Lehmann, G. G. Scherer. A. Wokaun, Y. Tasaki. Y. Ichikawa. K. Shinohara Application of High Resolution Neutron Imaging in Polymer Electrolyte Fuel Cells (PEFC) Diagnostics,. (ICTPS Conference on "From Physical Understanding to Novel Architectures of Fuel Cells". Trieste, Italy, May 21-25, 2007. «
K Tajiri, Y Tabuchi and C Y Wang "Isothermal Cold Start of Polymer Electrolyte Fuel Cells" Journal of Electrochemical Society, Vol. 154, pp. B147-B152, 2007. X
L Mao. C Y Wang, and Y. Tabuchi "A Multiphase Model for Cold Start of Polymer Electrolyte Fuel Cells" Journal of Electrochemical Society, Vol. 1 54, DD. B341-B351, 2007. X
K. Tajiri, Y. Tabuchi, F. Kagami, S. Takahashi, K. Yoshizawa. and C-Y. Wang "Effects of Operating and Design Parameters on PEFC Cold Start" Journal of Power Sources, Vol. 165, pp. 279-286. 2007. X
S Wang, Y. Utaka, Y. Tasaki Basic Study on Humidity Recovery by Using Micro-Porous Media [Effect of Thermal Conductivity of Materials on Transport Performance! Transactions of the Japan Society of Mechanical Engineers Part B. 19, 13451352. 2007. «
S. Takaichi, H. Uchida, M. Watanabe Response of Specific Resistance Distribution in Electrolyte Membrane to Load Change at PEFC Operation J. Electrochem. Soc.. 154. B1373-B1377, 2007. X
S. Takaichi, H. Uchida, M. Watanabe Distribution Profile of Hydrogen and Oxygen Permeating in Polymer Electrolyte Membrane Measured by Mixed Potential Electrochem. Comm.. 9, 1975-1979. 2007. X
S. Takaichi, H. Uchida, M. Watanabe Distribution Profile of Specific Resistance in Polymer Electrolyte Membrane During Load Change for PEFC ECS Trans 11 (1), 1505, 2007. X
M. Uchimura, S. Kocha The Impact of Cycle Profile on PEMFC Durability ECS Trans 11 (1!, 1215. 2007. X
A.Ohma. S.Yamamoto, K.Shinohara Analysis of Membrane Degradation Behavior During OCV Hold Test ECS Trans. 11 CD. 1181, 2007. X
T.Mashio. A.Ohma. S.Yamamoto. K.Shinohara Analysis of Reactant Gas Transport in a Catalyst Layer ECS Trans. 11 (1), 529, 2007 X
K. Tajiri, Y. Tabuchi, and C-Y. Wang Water and Methanol Crossover in Direct Methanol Fuel Cells - Effect of Anode Diffusion Media Electrochimica Acta. Vol. 53, pp. 55175522. 2008. X
X.G Wang. Y. Tabuchi. F Kagami and C-Y. Wang Durability of Membrane-Electrode Assemblies Under Polymer Electrolyte Fuel Cell Cold-Start Cycling Journal of the Electrochemical Society. Vol. 155, pp. B752-B761, 2008. X
K. Yoshizawa, K. Ikezoe. Y. Tasaki, D. Kramer, E. Lehmann, G. Scherer Analysis of Gas Diffusion Layer and Flow-Field Design in a PEMFC Using Neutron Radiography J. Electrochem. Soc.. 155. B223-B227, 2008. X
Y. Utaka, Y. Tasaki. S Wang. T. Ishiji and S. Uchikoshi Method of measuring oxygen diffusivity in microporous media NIHON Kikaigakkai Ronbunshyu (B) Vol.74. No.739, pp.655-661, 2008. X
S. Takaichi, H. Uchida, M. Watanabe In situ Analysis of Oxygen Partial Pressure at the Cathode Catalyst Layer/Membrane Interface During PEFC Operation Electrochim Acta, 53, 4699-4705. 2008 X
A.Ohma. S.Yamamoto, K.Shinohara Membrane Degradation Mechanism During Open-Circuit Voltage Hold Test J. Power Sources.182. 39-47, 2008. X
Y. Nagahara, S. Sugawara, K. Shinohara The Impact of Air Contaminants on PEMFC Performance and Durability J. Power Sources. 182. 422-428. 2008. X X
M. Uchimura, S. Sugawara, Y. Suzuki. J. Zhang, S Kocha Electrocatalyst Durability under Simulated Automotive Drive Cycles ECS Trans 16 (2), 225, 2008 X
T.Mashio, A.Ohma, S.Yamamoto, K.Shinohara Advanced In—situ Analysis of Reactant Gas Partial Pressure at Catalyst Layer/PEM Interfaces ECS Trans 16 (2), 1009, 2008. X
H.lden, A.Ohma, K.Shinohara Analysis of Proton Transport in Pseudo Catalyst Layers ECS Trans 16 (2), 1751, 2008. X
Genady Ragoisha. J. Zhang, S. Kocha. A. liyama Characterisation of the electrochemical redox behavior of Pt electrodes by potentiodynamic electrochemical impedance spectroscopy J.Solid State Electrochemistry, Voll4, 4, 531-542. 2010 X
Z Xie, T. Navessin, X Zhao, M Adachi, S Holdcroft, T. Mashio, A. Ohma, and K. Shinohara Nafion lonomer Aggregation and its Influence on Proton Conduction and Mass Transport in Fuel Cell Catalyst Layers ECS Trans. 16 (2), 1811, 2008. X
T. Mashio. K. Malek, M. Eikerling Microstructure of Catalyst Layers in Polymer Electrolyte Fuel Cells Redefined: A Computational Approach Journal of Chemical Physics X X
X.G Wang. Y Tabuchi, F Kagami and C Y Wang Cold-Start Durability of Membrane-Electrode Assemblies Handbook of Fuel Cells. Vol. 6, Chpt. 59, pp. 880-892. John Wiley and Sons, 2009. X
S. Sugawara. T. Maruyama. Y. Nagahara, S. Kocha. K. Shinohraa, K. Tsujita. S. Mitsushima, K Ota Performance Decay of Proton-Exchange Membrane Fuel Cells under Open Circuit Conditions Induced by Membrane Decomposition J. Power Sources. 187 324-331. 2009. X
S. Yamamoto. S. Sugawara, K. Shinohara Fuel Cell Stack Durability for Vehicle Application Fuel Cell Handbook in: Polymer Electrolyte Fuel Cell Durability, F. Büchi, M. Inaba and T. Schmidt :eds.:, Springer. 2009. X
N. Takimoto. S. Takamuku, M. Abe, A. Ohira, He-S Lee, J. E. McGrath. Conductive area ratio of multiblock copolymer electrolyte membranes evaluated by e-AFM and its impact on fuel cell performance Journal of Power Sources 194 662-667. 2009 X
1. Takahashi and S. Kocha Examination of the Activity and Durability of PEMFC Catalysts in Liquid Electrolytes Journal of Power Sources 195 6312-6322, 2010. X
Y. Utaka, D. Iwasaki, Y. Tasak and S Wang Oxygen Diffusion Characteristics of Gas Diffusion Layers With Moisture Heat Transfer-Asian Research Volume 39, Issue 4, pages 262-276, June 2010 «
Table 3
List of presentation (1)
AuthWS Title Journals. Workshop. Symposium, Conference Macro Mass Transport Meso-Micro Mass Transport Dgradatron Reaction
H. Nakamiya, K Kikuta. V. Tabe. T. Chikahisa. F. Kagami and K. Yoshizawa Study on Freezing Phenomenon in Polymer tlectrolyte Fuel Cell below Freezing Nrhon Kikai Gakkai Nenji Taikai Koen Ronbunshu. 275-276, 2005. x
K Yoshizawa, K IKezoe, K Shinohara. D. Analysis of Different Gas Diffusion Layer Materials in Fue) Ceis Nihon Kikai Gakkai Nenji Taikai Koen Ronbunshu. 277-27$. 2005. X
A Ohm». S Suga. S Yamamoto and K Shinohara Phenomenon Analysis of PFFC for Automotive Use [1; Membrane Degradation Behavior During OCV Hold Test 73th Meeting of The Electrochemical Society of Japan, abstract. P412. 2006 X
K. Yoshizawa. K Ikezoe. K Shinohara. D. Kramer and E. Lehmann and G. G Scherer Analysis of gas diffusion layer and flow-field design in a PEMFC using neutron radiography 13th Battery Symposium. B27. 238-241. 2006 X
fl.Ohma, S.Suga. S.Yamamoto, K.Shinohara Membrane Degradation Behavior during OCV Test GfiC, Fuel Cells. Rl. USA. 2006. X
K Kikula. H Nakamiya, Y. Tabe. T Chikahisa, F. Visualization of Freezing Phenomenon in Polymer Electrolyte Fuel 43th National Heat Transfer Symposium, 367-368. 2006 *
M Katsuta, T Sato, K Tamura, T. Hirai and N Kubo Evaluation of Water Transport Properties in a Polymer Electrolyte Membrane lor PEFC 43th National Heat Transfer Symposium, 321-322. 2006 X
Y Tabe. H. Nakamiya. K. Kikuta. T. Chikahisa. F. Kagami. K. Yoshizawa STUDY ON FREEZING PHENOMENA IN РЕМ FUEL CELL BLOW FREEZING 13th International Heat Transfer Conference. Sydney. Australia. 2006 Д
T. Maruyama. A. Ohma. $, Yamamoto and K. Shinohara Phenomenon Analysis of PEFC for Automotive Use (2) Membrane Degradation Behavior During OCV Hold Test Fall Meeting of The Electrochemical Society of Japan, 2006 x
A, Ohma. S. Suga. S. Yamamoto and K. Shinohara Phenomenon Analysis of PEFC for Automotive Use !1: Membrane Degradation Behavior in OCV Test Fall Meeting of The Electrochemical Society of Japan, 2006 x
A Ohma. S Suga, S. Yamamoto. K Shinohara Membrane Degradation Behavior during OCV Test 210th ECS transactions Vol. 3. 519-259, 200G X
K. Yoshizawa. K. Ikezoe. Y. Tasaki. 0. Kramer. E. H Lehmann, G, G Scherer Analysis of Gas Oiffsion Layer and Flow Field Design using Neutron Radiography 210th ECS transactions Vol 3. 397-407, 2006 j Eledrochem Soc.V 155, Issue 3, pp B223-227. 2008 я
T, Sasabe. N. Ueda. N, Kubo and J, Kusaka Analysis of oxygen transport-imited process of PEMFC under high current density operation Proceedings of Thermal Engineering Conlerence. PAGE.37-38, 2006. X
P, Bei Hat, 0 Kramer, B. C. Seyfang. G, Frei. L Lehmann, G. G Scherer, A Wokaun, Y. Tasaki, Y Ichikawa. K. Shinohara Application ol High Resolution Neutron Imaging in Polymer Electrolyte Fuel Cells (PEFC! Diagnostics ICTP. May, 2007 X
K. Fukui. H. Nakamiya. K. Kikuta. Y. Tabe. T. Chikahisa. S Takahashi and K Yoshizawa Cold-start Characteristics and Freezing Phenomena in РЕМ Fuel Cell below Freezing 44th National Heat Transfer Symposium in Nagasaki '2007; 1
S. Takita, M. Tsushima, S Hirai. K Aotani and N Kubo Magnetic Resonance Imaging of a Polymer Electrolyte Membrane under Water Permeation 44th National Heat Transfer Symposium in Nagasaki '2007;. Experimental Heat Transler, Volume 22, Issue 1 January 2009 . panes 1-11 x X
M Katsuta, K Tamura. T Hirai, X Sasabe. T Hara. K. Aotani and N Kubo A Study on Water Permeation Phenomena in Polymer Electrolyte Membrane lor PEFC 44th National Heat Transfer Symposium in Nagasaki !2007: x X
S Wang. Y. Utaka Y. Tasaki. Mochimaru and 0. Iwasaki Oxygen Diffusion Characteristics in Wet Gas Diffusion Layer for Fuel Cel 44th National Heat Transfer Symposium in Nagasaki '2007; x
T. Chikahisa. Y. Tabe. K. Kikula. H. Nakamiya. S. Takahashi and K Yoshizawa Study on Cold-Start Characteristics ol PEMFC below Freezing ASME 2007. NewYork x
Y lltaka, S Wang, and Y Yasaki Measurement if Oxygen Diffusion Characteristics of Porous Media Used for Gas Diffusion Layer of PEMFC 2007 ASME-JSME Thermal Engineering Conference, Vancouver, Canada x
S. Sugawara Degradation Analysis of Membrane Electrode Assembly GRC. Fuel Cells. 2007. Hi. USA x
A.Ohma. T.Hashio. S.Yamamoto. K.Shinohara Analysis ol Reactanl Gas Transport in a Catalyst Layer GRC. Fuel Cells. Rl. USA. 2007 x
Y. Nagahara. S. Sugawara The Impact ol Atmospheric Contaminants on PFMFC Performance and Durability International Workshop on Degradation Issues in Fuel Cells, Crete, Greece, 2007 x x
A Ohma. S. Yamamoto and K. Shinohara Phenomenon Analysis of PEFC lor Automotive Use f3l Membrane Degradation Behavior During OCV Hofd Test Fall Meeting of The Electrochemical Society of Japan, 2007 x
K Tsujita. S Sugawara. S Mtlsushima and K Ota Effect of Trace Anion on Oxygen Reduction Activity ol PI Catalyst Fall Meeting of The Electrochemical Society of Japan, 2007 x
II A Gaslei ger, S. S Kocha, F Wagner. R N Carter Artifacts in Measuring Eteclrode Catalyst Area of Fuel Cells through 212th ECS. Washington DC. USA, 2007. X
A. Ohma. $. Yamamoto, K. Shinohara Analysis of Membrane Degradation Behavior during OCV Hofd Test 212th ECS Washingon DC. Proceeding, 2007. X
T. Mashio. fl. Ohma. S. Yamamoto, K Shinohara Analysis ol Reactanl Gas Transport in a Catahst Layer 212th ECS Washingon DC. Proceeding. 2007. X
K. Tajifl, Y. Tabuchi and C-Y Wang Factors impacting gas purge in PEFCs 212th ECS Washingon DC. Proceeding. 2007. 1
F Jiang. W Fang, C-Y Wang. Y Tabuchi Non-isothermal coWslart of PEFCs 212th ECS Washingon DC. Proceeding 2007 x
M. Uchimura. S. Kocha The Impact ol Cycle Profile on PEMFC Durability 212th ECS Washingon DC. Proceeding. 2007. x
5 Takaichi, H Uchida, M Watanabe Distribution Prolite ol Specific Resistance in Polymer Electrolyte Membrane During Load Change for PEFC 212th ECS Washingon DC. Proceeding 2007 x
p. ßoillat. D Kramer, B. C. Seyfang. G. Frei. E Lehmann. G. G. Scherer, A. Wokaun. Y. Tasaki. Y. Ichikawa. K. Shinohara Application ol High Resolution Neutron Imaging in Fuel Cells Diagnostics ECNS07. Bilbao. Spain. 2007 X
M, Uchimura. S, Kocha The Impact ol PI Oxide Coverage on the Measurement of Durability Diagnostic Parameters 2007 AiChE Annual Meeting, Salt Lake City, Utah. USA X X
T. Sasabe. K. Yoshida. H. Kusaka. N. Kubo and K Aotani The Effects ol Cathode Flow Distributor Geometries on the Perlormance ol PEMFCs Theimal Engineering Conference 2007. Kyoto x
Y, Tasaki. S, Wang. Y. Ichikawa. 0, Kramer. P, ßoillat. G Frei. G G Scherer and E. H Lehmann. Y. Utaka and 0. iwasaki Oxygen Diffusion Characteristics tor Wet Gas Diffusion Layer (further report) Thermal Engineering Conference 2007, Kyoto X
S. Miyazaki. T. Kaitoh. N. Kubo and M. Katsuta Measurement of water transport properties of Plymer Electrolyte Membrane -Measurement of Electro-osmotic drag coefficient - 45th National Heat Transfer Symposium in Tsukuba (2008; x
K Aotani, S Miyazaki, T Kaitoh, N Kubo and M. Katsuta Measurement of water transport properties of Plymer Electrolyte 45th National Heat Transfer Symposium in Tsukuba i200# X
Y, Tasaki. Y Ichikawa, N Kubo, K Shinohara. P Borllat. D Kramer. G G Scherer and E H Lehmann In situ diagnostic ol waler distribution in thickness direction of MEfl by neutron imaging - focused on characteristics ol water distribution of gas diffusion layer - 45th National Heat Transfer Symposium in Tsukuba ;2ooa; x
0 Iwasaki, Y. Utaka, 1. Hirose. Y. Tasaki and S. Wang Oxygen Dillusion Characteristics of Gas Diffusion Layer with Moisture - visualization ol iiguid water in gas diffusion layer by к ray - 45th National Heat Transfer Symposium in Tsukuba :2dos: x
1, Hirose. Y, Utaka. 0. Iwasaki. Y. Tasaki and S. Wanq Oxygen Diffusion Characteristics of Gas Diffusion Layer with Moisture 45th National Heat Transfer Symposium in Tsukuba 2008: x
Y Tabuchi. N Kubo The impact ol Rib/Channel, water and heat transport on limiting current density 6th ASME Fuel Cel Conlerence. Den vor. USA. 2OOS. i
T. Mashio, A. Ohma, K. Yamaguchi. K. Shinohara. K^ Malek Nano-scale ModeSng of Catalyst Layers for РЕМ Fuel Cells ISTCP, Vancouver. CAN. 2008 X
3 Kocha lulhjeuce ol Oxides on the Activity and Uurabilily ol PtMl-L GRC, Fuel Cells, 2008, Rl. USA x
H.lden, A.Ohma, K.ShinOhara Analysis ol Proton Transport in Pseudo Catalyst Layers GRC, Fuel Cells, 2008, Rl. USA X
Y. Tabuchi, S. Takaichi, and N Kubo The impact ol Rib,'Channel, water and heat transport on limiting GRC, Fuel Cells. 2008, Rl. USA X
Y Suzuki, S Sugawara, N Horibe, 5 S Kocha, K, Shinohara MFA Performance 1-D Modeling for Analysis of Kinetic Loss in Catalyst Layer GRC. Fuel Cells. 2008. Rl. USA x
S. Kuwala. S. Sugawara. K. Shinohara, S S. Kocha Investigation of Hydrogen Oxidation Reaction Mechanism in Liouid Electrolytes and MEAs GRC. Fuel Cells. 2008. Rl. USA X x
M, Uchimura. S. S. Kocha The Influence of Pt-Oxide Coverage on the ORR Activity and Reaction Order in PEMFCs GRC. Fuel Cells. 200S. Rl. USA X
S, Sugawara. S, Kocha. K, Shinohara. K. Tsujita, S Mitsushima and K 01a Performance Modeling lor Breakdown of Catalyst Layer Polarization Component GRC. Fuel Cells. 2008. RL USA X
International Scientific Journal for Alternative Energy and Ecology № 9 (89) 2010
© Scientific Technical Centre «TATA», 2010
Table 4
List of presentation (2)
Authors Tttto Journals, Workshop, Symposium. Conference Macro Mass Transport Mcso-Micro Mass Transport Dgradalion Reaction
V. Tasaki, S. Wang. P. Boillat, 0. Frei. 0. 0. Scherer. E. H Lehmann. Y. Utaka and D. iwasaki Oxygen Diffusion Characteristics of Mieroporous Media with Moisture - Simultaneous measuring oxygen diliusivlty and Equld water Annual Meeting of JSME, Yokohama. 2008. i
T. Mashio. A. Ohma, K Yamaguehi and K. Shinohara Molecular dynamics study of structure and transport properties of polymer electrolyter in a catalyst layer The Sixth Congress of ISTCP ISTCP VI:, 2008. X
K. Aotani. N. Kubo, K Kamiguchi and H Sato Water Transport Characteristics of Polymer Electrolyte Membrane for PEFC 57th Symposium on Macromolecules. Osaka. 2008 i
K. Kamiguchi. H. Sato. K, Aotani. S, Takamuku and N Matsuoka Characterization Ot water in polymer electrolyte membrane by using Of tH NMR spectroscopy b/lh Symposium on Mac romolec ules. Osaka. 2008 i
P. Boillat. M. H Bayer G, Frei. D. Kramer. E. H Lehmann. 6. G Scherer. 1. A. Schneider. B. C. Seylang. K. Shinohara. Y, Tasaki. A. Wokaun Recent pregress in Neutron Imaging of Liquid water in polymer Electrolyte Fuel Celts (PEFCs) 59th Annual Meeting of the International ot Society of Electrochemistry, Seville Spain. 2008, X
S. Kocha Influence of Oxides on the Activity and Durability of PEMFC Catalysis 214th ECS Meeting Honolulu. USA. 2008, X X
S Kocha Eteclrocatalyst Oorabifily under Simulated Automotive Drive Cycles 2141h ECS Meeting Honolub. USA, 2008 *
M, Uchimura. S, Sugawara, Y. Suzuki. J, Zhang. S S Kocha Eleclrocatalyst Durability under Simulated Automotive Drive Cycles 214th ECS Meeting Honolulu. USA. 2003. X
S. Sugawara. S. Kocha. K. Shinohara. K. Tsujita. S. Hit sushi,ma and K. Ola Simultaneous Electrochemical Measurement of Pt Oxide Coverage and ORR Kinetics 214th ECS Meeting Honolulu. USA. 2003, X
T. Horibe. S. Kocha and M. Kaseda Platinum Dissolution-deposition Phenomena during Potential Cycling in MEAs Ot PEMFCs 214th ECS Meeting Honolulu. USA. 2003. X
M Uchimura. S, S, Kocha The Influence of PI-Oxide Coverage on the ORR Reaction Order in PEMFCs 214th ECS Meeting. Honolulu. HI. USA. 2003 X
Y Suzuki. S Sugawara, N Horibe, S S Kocha. MFA Performance Modeling for Breakdown of Catalyst Layer 214th ECS Meeting, Honolulu, HI, USA, 2008 X
S Sugawara, K Tsujita. S S Kocha, K Shinohara. & Milsushima. K. Ola Simultaneous Electrochemical Measurement of ORR Kinetics and Pi Oxide Formation/fieduction 214th ECS Meeting Honolulu. USA. 2008 X
K. Tsujila. S Sugawara. S Milsushima and K Ota Effect of Trace Impurity for Oxygen Reduction Reaction on Pt Catalyst 214th ECS Meeting. Honolulu. HI. USA, 200a X
K. Tsujila. S Sugawara. S Kocha, K, Shinohara. S Milsushima and K Oia Simultaneous Electrochemical Measurement of Pt Oxide Coverage and ORR Kinetics 214th ECS Meeting Honolulu, USA, 2008 x
214th ECS Meeting Honolulu. USA. 2008.
T Mashio, A Ohrna, K Yamaguehi and K.Shinohara Advanced In-situ Analysis 214th ECS Meeting Honolulu. USA. 2008. X
Z Xie. T Navessin. X. Zhao. M Adaehl. S Hotdcroft. T, Mashio. A, Ohma. and K, Shinohara Nation lonomer Aggregation and its Influence on Mierostrueture and Proton Conduction in Fuel Cell Catalyst Layers 214th ECS Meeting Honolulu. USA. 2008. X
Y Tahuchi S Takaichi and N Kubo Limmiling Current Density Under Low Humidity Condition 2141h ECS Meeting Honolulu, USA, 2008 t
2141 h ECS Meelina Honolulu. USA. 2008.
K. AotanL S liyazati, N. Kubo and M. Katsuta AN ANALYSIS OF THE WATER TRANSPORT PROPERTIES OF POLYMER ELECTROLYTE MEMBRANE 214th ECS Meeting Honolulu. USA, 2008. X
M Yaginuma, T Himeno, A Miyazawa and T. Aral Sensitivity evaluation of metaric ions to degradation on cell performance 491h Battery Symposium. Sakai. 2008 X
H. Iden, A Ohma and K. Shinohara Analysis ot proton transport in pseudo catalyst layers 491 h Battery Symposium. Sakai, 2008 x
T, Shiomi and Y. Tabuchi The analysis ot celt vottage droc under high fuel utilization condition 49th Battery Symposium. Sakai. 2008 X
0 Aofci. Y. Tasaki. P Bollat. E Lehmann. G Measurement ot Water Content Distribution in MEA by Neutron 49th Battery Symposium, Sakai. 2008 X
S. Tsurumolo. S. Takita. M Tsushima. S. Hirai, K. AotanL Y. Tabuchi and N. Kubo Measurement ot Wafer Transport in Polymer Electrolyte Membrane by Magnetic Resonance Imaging 491h Battery Symposium, Sakai, 200S X
S Miyazaki. Y Tabuchi. K Aotani. N Kubo and M Katsuta The Eflecl ot net wafer transport through the membrane on PEFC performance at high current density operation 491 h Battery Symposium, Sakai. 2008 x
H. Yoshimura. Y. Ishikawa. H. Kusaka, K. Aotani. Y Sij?ue and N Kubo Measurement ot thermal resistance and temperature under operation in MFA for PEFC 491 h Battery Symposium. Sakai. 2008 x
K, Satoh. A, Oh ma. K, Yamaguehi and K, Shinohara Analysis ot Water Transport Phenomena in Catalyst Layers 76lh Meeting ol The Etectiochemical Society Japan. Kyoto. 2009 x
K, Sakai. R, Satoh. T. Mashio. A, Ohma. K. Yamaguehi and K. Shinohara Analysis ot reaclanl gas transport phenomena in catalyst layers 76th Meeting ol The Electrochemical Society Japan. Ryoto. 2009 i
A. Miyazawa. R. Ikezoe. Y. Okuyama and M. Yanagisawa The Development of High Power Density and Low Cost New Fuel Cei Slack 2009 JSEA Spring Meeting. Yokohama X
T.Mashio. A Ohma. K Yamaguehi, K.Shinohara. K.Maleh Molecular Dynamics Study ot Catalyst Layers lor PEM Fuel Cells 71h ISE Spring Meeting. Szczyrk. Poland 2009, X
Y. Tabuchi. N. Kubo and K. Shinohara The Effect of Rib Channel Geometry on Cell Performance under Hgh Current Density GftC. Fuel Cels. 2009, Rl. USA X
T Mashio. A. Ohma, H Kanesaka and R. Shinohara A Molecular Dynamics Study of Adsorbed lonomer and Water on Carbon Support GRC, Fuel Ceis, 2009. Rl, USA X
K. Sato. T. Mashio, A. Ohma. K. Yamaguehi. K. Shinohara Analysis of Water Transport in Catalyst Layers 2151b ECS. San Franslsco, USA. 2009. x
R Fu and * Tabuchi An Investigation of Thermaly-Induced Waler Transport in Polymer Electrolyte Fuel Celts with Neutron Radiography Imaging Technique 2161b ECS. Vienna. Austrl, 2009 X
A Ohma. K Sakai. K Yamaguehi and K. Shinohara Analysis ot reactant gas transport phenomena in catalyst layers 216th ECS. Vienna, Austri, 2009. X
A Ohma, H Iden. K Yamaguehi and K Shinoha'a Analysis of proton transport in pseudo catalyst layers Influence of ionomer content- 2161b ECS. Vienna. Austri. 2009 X
A. Ohma. K. Satoh. K Yamaguehi and K Shinohara Analysis ot Water Transport Phenomena in Catalyst Layers -the Effect of Carbon Supports- 216th ECS. Vienna. Austri. 2009 x
Y Tabuchi. N Kubo and K Shinmohara The Eflecl of Heat and Water Transport on Cell Performance under High Current Density Operation ASME 7th International Fuel Cell Science. Engineering & Technology. USA. 2009. X
0. Aoki, Y Tasaki. P Boillat, E Lehmann. G Scherer Measurement of Wafer Content Distribution across the MEA by Neutron Radiography ASME 7th International Fuel Cell Science, Engineering St Technology. USA. 2009. X
A Ohma. T. Mashio. Y. Ono. R. Satoh Estimation ol in-situ Pt utilization ot a cathode catalyst layer for PEMFC Fall Meeting ol The Electrochemical Society Japan. Tokyo. 2009 X
Y. Ono, A. Ohma. H. Kanesaka and K. Shinohara Estimation ol in-situ Pt utilization ol a cathode catalyst layer for PEMFC Fall Meeting ol The Electrochemical Society Japan, Tokyo, 2009 x
H. Tanaka. S. Sugawara. S. Kuwata. M. Uchimura and K Shinohara Durabirity evaluation and behavior ol efeclrocatalysls of automotive fuel cell 50th Battery Symposium. Kyoto. 2009 X
T. Itoh. K. Jinnai. H. Tanaka. M. Uchimura. S Sugawara and K. Shinohara A Degradation Mechanism of a automotive fuel cell electrode studied by transmission electron micrography 50th Battery Symposium. Kyoto. 2009 X
H. Iden, A. Ohma, H. Kanesaka and K. Shinohara Analysis of proton transport in pseudo catalyst layers -Influence of ionomer content - 501h Battery Symposium. Kyoto. 2009 X
Y. Ono, A. Ohma. H. Kanesaka and K. Shinohara Estimation of In-situ Pt utilization ol a cathode catalyst layer for PEMFC 50tb Battery Symposium. Kyoto. 2009 X
A. Ohma. S Ichiya. K. Fushinobu and K. Okazaki Oxygen Reduction Reaction Paths and Behavior of Hydrogen Peroxide Formation on PI '111: for PEMFC 461b National Heat Transfer Symposium in Kyoto. 2009. X
M Tsushima. S. Tsurumolo, S. Takita. S. Hirai, Y. Tabuchi. N. Kubo and K. Aotani Water diffusion and interfacial mass transfer under water permeation in a polymer electrolyte membrane 461 h National Heal Transfer Symposium in Kyoto, 2009. X
M Kalsuta. H Yamakawa. K Watanabe. Y A Sludy on Water Permeation Phenomena in Polymer Electrolyte 461h National Heat Transfer Symposium in X
Y. Tasaki. A. Aoki. T. Miyata. Y. Utaka. D. Iwaaaki. S. Rondo and Y. Aoki visualization of Liquid Water In Micro Porous Media with Addition of Pore Size Distribution by using X-ray radiography 46th National Heat Transfer Symposium in Kyoto. 2009. X
D, Iwasaki. Y, Utaka and Y. Tasaki Measuring Method for Apparent Oxygen Diflusivity of Mtcroporous Media with Moisture 46lh National Heal Transfer Symposium in Kyoto, 2009 X
Table 5
List of presentation (3)
Authors Title Journals, Workshop. Symposium. Conference Macro Mass Transport Meso-Micro Mass Transport Dgradation Reaction
Y Tabuchi, T. Shiomi, A. Aoki, N. Kubo and K. Shinohara Rib/Channel Eltect on Cell Performance under High Current Density Operation ASME 8th international Fuel Cell Science, Engineering & Technology, NY, USA. 2010 X
T. Shiomi. R. S. Fu, U. Pasaoguilari. S. Miyazaki, Y Tabuchi, N. Kubo, K. Shinohara, D. S. Hussey, D. L. Jacobson Analysis ol the effect of liquid water saturation on oxygen transport inside the GDI ASME 8th international Fuel Cell Science. Engineering & Technology, NY. USA. 2010. X
T Suzuki, Y Tabuchi, K. Aotani and N. Kubo Measurement of water content distribution in catalyst coated membrane at water permeation condition by magnetic resonance imagin ASME 8th international Fuel Cell Science. Engineering & Technology, NY, USA. 2010. X
T Shiomi. S. Miyazaki, Y. Tabuchi. N. Kubo, K. Shinohara The effect of liquid water saturation on oxygen transport inside the GDI ASME 8th international Fuel Cell Science. Engineering S Technology, NY, USA. 2010. X
R. S. Fu. T. Shiomi, Y. Tabuchi. N. Kubo and K. Shinohara Effect of liquid water saturation on water transport through polymer electrolyte fuel cells ASME 8th International Fuel Cell Science. Engineering & Technology, NY, USA. 2010 X
T Mashio, A, Ohma, H. Kanesaka and K. Shinohara A Molecular Dynamics Study of lonomer and Water Adsorption at Carbon Support Materials 217th ECS. Vancober. Canada. 2010. X
Y Ono, T Mashio. A Ohma, S. Takaichi, H Kanesaka and K. Shinohara The analysis of performance loss with low platinum loaded cathode catalyst layers 217th ECS, Vancober, Canada, 2010. X
S. Kuwata. S. Sugawara. K. Shinohara. M. Shirai and A. Fujiki Electrochemical properties of graphite intercalated platinum nanosheets as catalyst for automotive fuel cell Spring Meering of Japan Society of Powder and Powder Metallugy. 2010. X
Y. Tabuchi. T. Shiomi. 0. Aoki and N. Kubo Effect of rib/channel geometry on cell performance under high current density operation 47th National Heat Transfer Symposium in Hokkaido. 2010. X
T Suzuki, Y. Tabuchi. K. Aotani. N. Kubo, M. Tsushima and S, Hirai Effects of catalyst layer on water transport in PEM under non-equilibrium condition of humidity 47th National Heat Transfer Symposium in Hokkaido. 2010, X
Y. Kimura. G. Inoue. Y. Matsukuma, M. Minemoto. 0. Aoki and N. Kubo Simulation of liquid water evaporation in GDL for PEMFC 47th National Heat Transfer Symposium in Hokkaido. 2010. X
G Inoue, Y. Kimura. K Jyonouchi. N ishibe, Y. Matsukuma. M. Minemoto. 0. Aoki and Y. Tabuchi Effect of PTFE treatment on GDL liquid water condition 47lh National Heat Transfer Symposium in Hokkaido. 2010. X
S, Takahashi. Y. Fukuyama, Y. Tabuchi and N Kubo Effect of water transport capability on frost formation in catalyst laver under sub-zero operations 47th National Heat Transfer Symposium in Hokkaido. 2010. X
T Sakai, M. Katsuta, K Watanabe. K Aotani and N. Kubo Measurement of the water content and the water transport properties of PEM under water permeation process 47th National Heat Transfer Symposium in Hokkaido. 2010. X
S. Takada, Nakagaki, Yoshimura, Kusaka, Adachi. Suzue. Aotani. Kubo Measurement of thermal resistance and temperature under operation in MEA for PEFC 47th National Heat Transfer Symposium in Hokkaido. 2010. X
K. Sakai, A. Ohma, H. Kanesaka and K Shinohara ln-situ measurement of reactant gas diffusion coefficient in catalyst layers 77th Meeting of The Electrochemical Society Japan, Toyama, 2010 X
Fujita. Mitsushima, Ota. Nagahara. Sugawara, Shinohara Simultaneous evaluation of ORR kinetics and Pt oxidation-reduction using RRDE 77th Meeting of The Electrochemical Society Japan, Toyama. 2010 X
T Shiomi, Y. Fukuyama, S. Miyazaki, Y. Tabuchi, N. Kubo and M. Sakai Oxygen Transport Resistance Induced by Rib/Channel Geometry GRC, Fuel Cells, 2010, Rl, USA X
Y Nagahara. K. Arihara. S. Sugawara and K. Shinohara Evaluation of S02 Tolerance of Pt-based Electrocatalysts GRC, Fuel Cells. 2010, Rl. USA X
4 Summary
The results of the analyses and investigations described here have shown that the power generation characteristics of fuel cell systems are substantially influenced by the flow channel geometry, catalyst surface state and also the configuration of the MEA and the properties of its individual constituent materials. The respective influence of each of these factors and the mechanisms involved are also steadily becoming clear. In order to promote the practical use of FCVs in the coming years, it will be necessary to have a more exact understanding of the governing factors of various complex phenomena that occur simultaneously and in a synchronized manner inside the fuel cell system. In terms of size, the phenomena range from the microscale to the macroscale level. With respect to time, they range from the picosecond level of electrochemical reactions to a level of seconds or minutes for transport processes and state changes. The resultant knowledge needs to be reflected in better material designs and cell structures. In order to understand the phenomena accurately, it will be increasingly important to apply more precise computational science methods and experimental analyses in a complementary manner. Accordingly, it is hoped that further advances will be achieved in the analytical methods mentioned here in order to support such efforts.
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© Scientific Technical Centre «TATA», 2010
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