Chapter 6 General Conclusions and Future Prospects
6.2 Future prospects
The usability of these visualization systems were demonstrated in this study. As a further improvement of segmented see-through PEFC, transparent electroconductive materials, e.g. indium tin oxide (ITO), are expected to be used for the current collector.
Using transparent current collectors permits a more detailed comparison of p(O2) and the current density. The reduction of the contact resistance between the transparent current collectors and the current wires could be a problem to be solved.
The following subjects are expected for the further useful information:
(i) Visualization under various operating conditions (transient phenomena, different flow rates, different humidities at the anode and the cathode, use of dry gases, different gas-flow directions and reactants with contaminants etc.) (ii) Various MEA components (hydrocarbon mambranes, lower catalyst loadings
and GDL structures etc.)
(iii) GFC geometry (channel structure, depth and rib width etc.) (iv) Computational simulation.
For (i), various operating conditions and transient phenomena are the key factors.
The distribution of p(O2), the current density and the water droplets was visualized at quasi-steady state in this thesis, but this system can be used with the time resolution of 100 ms. Transient changes inside the cell, such as a sudden load change at the cell start/stop, the acceleration and the deceleration, are important to reveale the dynamic reaction distributions inside PEFCs. The commercial FCVs are using the counter flow configuration with no humidifier. The use of dry gases and change of the gas flow directions are needed to be investigated for more uniform reaction distributions. In addition, the operating modes, such as flowing and stopping modes, should be investigated. For (ii), the properties of the membranes, such as the proton conductivity and the mechanical stability, strongly depend on the water contents.
Therefore, the visualization of reaction distribution using different types of membranes would provide valuable information to be feed-backed directly to the synthesis. For (iii), p(O2) under the ribs was lower due to the lower gas diffusivity.
However, under the ribs near the GFC curves, p(O2) was higher as explained in
76
Chapter 3. Using the narrow ribs and the GFC structure allowing an effective gas supply under the ribs would improve the homogeneity of the reaction distributions.
For (iv), the combination of the experimental results with the computational simulation will provide a deeper understanding of the reaction distributions and the mass transports throughout the cell. Moreover, I suppose this system can be used as a diagnosis tool to detect the failed MEA such as pinhol in membrane.
77
List of Publications
1. Simultaneous visualization of oxygen partial pressure, current density, and water droplets in serpentine fuel cell during power generation for understanding reaction distributions
Kazuhiro Takanohashi, Takeo Suga, Makoto Uchida, Toshihide Ueda, Yuzo Nagumo, Junji Inukai, Hiroyuki Nishide, Masahiro Watanabe, J. Power Sources 343 (2017) 135-141.
2. Visualization of the oxygen partial pressure on the gas-diffusion-layer surface under the single-serpentine flow channel and the ribs in a polymer electrolyte membrane fuel cell during the power generation
Kazuhiro Takanohashi, Makoto Uchida, Akihiro Iiyama, Junji Inukai, J. Surf.
Finish. Soc. Jpn. 68 (6) (2017), to be published.
78
Meeting Abstracts
1. “Simultaneous Visualization of Oxygen Partial Pressure and Current Density in PEFC during Operation”
K. Takanohashi, J. Inukai, Y. Ishigami, M. Uchida, Y. Nagumo, H. Nishide, M.
Watanabe, 6th International Fuel Cell Workshop 2012 (IFCW 2012), P54, Kofu, Japan, August, 2012.
2. “Simultaneous Visualization of Oxygen partial pressure and Current density in PEFC”
K. Takanohashi, Y. Ishigami, Y. Nagumo, M. Uchida, J. Inukai, H. Nishide, M.
Watanabe, 80th Meeting of Electrochemical Society of Japan, 3C07, Sendai, Japan, March, 2013.
3. “Simultaneous Visualization of Oxygen Partial Pressure and Current Density during Operation of Fuel Cell”
K. Takanohashi, J. Inukai, M. Uchida, Y. Nagumo, T. Suga, H. Nishide, M.
Watanabe, The 2nd International Workshop on Green Energy Conversion, P28, Koumi, Japan, September, 2013.
4. “Simultaneous Visualization of Oxygen Partial Pressure and Current Density in Running PEFC”
K. Takanohashi, J. Inukai, M. Uchida, Y. Nagumo, T. Suga, H. Nishide, M.
Watanabe, The 224th Meeting of The Electrochemical Society, 1625, San Francisco, CA, USA, October - November 2013.
5. “Water Influence on Power Generation of PEFC Studied by Visualization of Oxygen Partial Pressure and Current Density”
K. Takanohashi, J. Inukai, M. Uchida, Y. Nagumo, T. Suga, H. Nishide, M.
79
Watanabe, The 3rd International Seminar on Green Energy Conversion, P65, Hokuto, Japan, August 2014.
6. “Water Influence Analyzed by Simultaneous Visualization of Oxygen Partial Pressure and Current Density inside PEFC during Power Generation”
K. Takanohashi, M. Uchida, T. Suga, Y. Nagumo, J. Inukai, H. Nishide, M.
Watanabe, 55th Battery Symposium in Japan, 1F28, Kyoto, Japan, November 2014.
7. “Mass Transport inside PEFC during Power Generation Studied by Visualization of Oxygen Partial Pressure and Current Density”
K. Takanohashi, M. Uchida, T. Suga, Y. Nagumo, J. Inukai, H. Nishide, M.
Watanabe, The 227th Meeting of The Electrochemical Society, 1639, Chicago, Illinois, USA, May 2015.
8. “Oxygen Partial Pressures inside Gas Diffusion Layer of Polymer Electrolyte Fuel Cell during Power Generation”
Y. Kakizawa, K. Takanohashi, M. Ihara, Y. Nagumo, T. Ohno, L. A. Nicolas, F.
Buechi, A. Iiyama, J. Inukai, 67th Annual Meeting of the International Society of Electrochemistry, s07-083, Hague, Netherlands, August 2016.
9. “Novel Segmented PEFC for Studying Mass Transport: Distributions of Oxygen Partial Pressure and Current Density during Power Generation”
K. Takanohashi, M. Uchida, J. Inukai, The 5rd International Seminar on Green Energy Conversion, P77, Koumi, Japan, August 2016.
80
Acknowledgments
For this thesis, researches have been carried out at Fuel Cell Nanomaterials Center, Clean Energy Center, and Interdisciplinary Graduate School of Medicine and Engineering in the University of Yamanashi.
I would like to express my greatest gratitude to Professor Junji Inukai of the University of Yamanashi, academic supervisor of this work, for his continuous guidance, invaluable suggestions, and warm encouragements throughout this work.
I would like to express my sincere thanks to Professor Makoto Uchida of the University of Yamanashi for his helpful suggestions, excellent technical advices and continuous guidance to this work.
I would like to express great acknowledgement to Professor Masahiro Watanabe for his valuable discussions and useful technical advices.
I sincerely appreciate Professor Hiroyuki Uchida of the University of Yamanashi for his valuable advices, valuable discussions and encouragements.
I would like to express great acknowledgement to Professor Akihiro Iiyama for his excellent advices, useful discussions, and encouragements through the experiment.
I also would like to express my gratitude to Professor Kenji Miyatake of the University of Yamanashi for his valuable discussions and technical advices.
I would like to express my sincere thanks to Professor Hiroyuki Nishide of Waseda University for his valuable discussions and encouragements as a research collaborator.
I would also like to thank Professors Masaharu Komiyama and Satoshi Wada of the University of Yamanashi, Professor Kim Hasuck of Daegu Gyeongbuk Institute of Science & Technology, Visiting Assosiate Professor Hiroshi Senoo of National Institute of Advanced Industrial Science and Technology (AIST) for the helps as the members of the advisory committee.
I would also like to thank Professors Shigehito Deki, Takao Tsuneda and Katsuyoshi Kakinuma for their beneficial suggestions to my study.
I am grateful to Professors Tomio Omata, Kazutoshi Higashiyama, Toshihiro
81
Miyao, Donald A. Tryk, Manuel E. Brito, Mitsuru Wakisaka, Shinji Nohara, Hiroshi Yano, Junpei Miyake, Hanako Nishino, Takeo Kamino of the University of Yamanashi, for their suggestions and warm encouragements.
I would also like to thank to express my sincere thanks to Dr. Takeo Suga of Waseda University for his helpful suggestion and excellent discussion as a coauthor of academic papers.
I would like to express great acknowledgements to Mr. Yuzo Nagumo, Mr. Takashi Ohno, Dr. Yuji Nakama and Mr. Masahiro Ihara of Shimadzu Corp., for their valuable discussions and technical advices. I also express my sincere thanks to Mr.
Toshihide Ueda (Panasonic Production Technology), Dr. Masakazu Yoneda (Mizuho Information & Research Institute, Inc.) and Mr. Haruhiko Motegi (Mizuho Information & Research Institute, Inc.) for their valuable discussions and technical advices.
I am grateful to Dr. Felix N. Büchi, Professor Thomas J. Schmidt, Dr. Jens Eller, Dr. Adrien N. Lamibrac, Mr. Michel Suermann, Mr. Martin Ammann, Mr. Thomas Gloor, Dr. Christian Peter, Mr. Florian Runtsch, Mr. Jonathan Halter and all of members of Pail Scherrer Institut for their kindly help and invaluable discussions.
I am grateful to Dr. Kenji Takada, Dr. Yuta Ishigami, Dr. Katsuya Nagase, Mr.
Takashi Kobayashi, Mr. Ichiro Nagata, Mr. Yu Kakizawa, Mr. Takeshi Kawamura and Mr. Toshiro Iwataki for their strong assistances to my study.
I am grateful to Dr. Hirotaka Hanawa, Dr. Jumpei Saito, Dr. Takuya Shimura, Dr. Kazuki Okaya, Dr. Takuya Omata, Dr. Satoki Hirakata, Dr. Jun Omura, Dr.
Takayuki Hoshi, Dr. Masaru Sakamoto, Dr. Naoki Yokota, Dr. Teppei Kawamoto, Mr. Tomohiro Akiyama, Dr. Takashi Mochizuki, Dr. Morio Chiwata and Dr. Yuji Chino for their helpful advices and valuable discussions.