Japan Science And Technology Research Articles

(Invited) Effect of Water Management in Membrane and Cathode Catalyst Layers on Suppressing the Performance Hysteresis Phenomenon in Anion-Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) are vulnerable to water management problems, since water is produced at the anode and consumed at the cathode. Previously we found severe voltage losses when increasing the current density in an AEMFC with a commercial Fe–N–Cp cathode catalyst and an in-house-developed anion exchange ionomer (quaternized poly(arylene perfluoroalkylene), i.e., QPAF-4, developed in this laboratory (Figure 1)1,2. In the present work,3 we have clearly identified the problem as being related to water management and developed two approaches to alleviating the problem: i) by use of a thin hydrophilized membrane, the diffusivity of water at the surface was improved, and the severe I–V hysteresis was suppressed, despite the cell using an Fe–N–Cp cathode catalyst with high-water absorption (Figs. 2a and 3a); ii) the voltage loss was also alleviated by the use of a recently developed Fe–N–Cc catalyst with higher hydrophobicity, which decreased the absorption of back-diffusing water into the catalyst layer and increased the amount of water supplied to the reaction sites. These improvements have demonstrated that water transport is the main limitation for the previously reported hysteresis and provide strategies to achieve higher performance AEMFCs through proper water management and formation of water transport pathways (Figs. 2b and 3b). Acknowledgements This project was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) Japan through funds for the “Advanced Research Program for Energy and Environmental Technologies,” by the Japan Society for the Promotion of Science (JSPS) and the the Swiss National Science Foundation (SNSF) under the Joint Research Projects (JRPs) program, and by the Japan Science and Technology (JST) through the Strategic International Collaborative Research Program (SICORP). We are grateful to Pajarito Powder supplying the Fe–N-Cp catalyst. Also, we are deeply grateful to Dr. Weilin Xu and Dr. Ping Song of Changchun Institute of Applied Chemistry and Dr. Shuanjin Wang of Sun Yat-sen University for supplying the Fe–N-Cc catalyst, and to Takahata Precision Co. Ltd. for kindly providing the QPAF-4 membrane and ionomer. References H. Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, Robust anion conductive polymers containing perfluoroalkylene and pendant ammonium groups for high performance fuel cells, J. Mater. Chem. A 5 (2017) 24804–24812, https://doi.org/10.1039/c7ta09409d.K. Otsuji, N. Yokota, D. A. Tryk, K. Kakinuma, K. Miyatake, M. Uchida, Performance hysteresis phenomena of anion exchange membrane fuel cells using an Fe–N–C cathode catalyst and an in-house developed polymer electrolyte, J. Power Sources, 487 (2021) 229407, https://doi.org/10.1016/j.jpowsour.2020.229407K. Otsuji, Y. Shirase, T. Asakawa, N. Yokota, K. Nagase, W. Xu, P. Song, S. Wang, D. A. Tryk, K. Kakinuma, J. Inukai, K. Miyatake, M. Uchida, J. Power Sources, 522 (2022) 230997, https://doi.org/10.1016/j.jpowsour.2022.230997 Figure 1

Effect of Water Management for Membranes and Catalyst Layers Using an In-House Developed Polymer Electrolyte on Cell Performance Hysteresis in Anion Exchange Membrane Fuel Cells

In this work, we focus on the water management challenges and report on the improvements of cell performance for anion exchange membrane fuel cells (AEMFCs) using an in-house-developed anion exchange ionomer (quaternized poly(arylene perfluoroalkylene), i.e., QPAF-4, developed in this laboratory (Figure 1).1 Previously, we investigated the I-V hysteresis observed in cells using the non-precious metal catalyst Fe-N-C and found the importance of water management. 2A thinner electrolyte membrane facilitates the diffusion of water due to OH⁻ movement, such as the use of back-diffusing water to the cathode, and is effective for water management in AEMFCs. As the electrolyte membrane, QAPF-4 (ion exchange capacity: IEC = 2.0 meq g-1) membranes with film thicknesses of ca. 10, 20 and 30 μm were used. Since this membrane is soluble in methanol, it is also suitable for use as an electrode binder. An MEA in which platinum was loaded (0.20 mgPt cm-2) on both the anode and cathode was prepared. Pt loaded on carbon black (Pt/CB, TEC10E50E), supplied from TKK Japan, was used as the platinum electrocatalyst.Figure 2 shows a comparison of the I-V performances for cells utilizing the various membrane thicknesses at 60 oC, 100% RH, 0 kPag; anode H2 (100 mL min-1); cathode O2 (100 mL min-1). The cells all exhibited I-V hysteresis, i.e., a large difference in potential between increasing and decreasing current densities (CDs) as the membrane thickness decreased. From Figure 3a-b, as a result of confirming the potential change between the anode and the cathode using a cell with a reversible hydrogen electrode (RHE) provided on the cathode side, we conclude that this hysteresis phenomenon mainly occurs at the anode. We are exploring the contributing factors and will provide further details in the presentation. From these results, we found that there is an important factor in the relationship between the anode and the electrolyte membrane in the development of high performance AEMFCs with efficient water management capability. Acknowledgement This project was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) Japan through funds for the “Advanced Research Program for Energy and Environmental Technologies,” by the Japan Society for the Promotion of Science (JSPS) and the the Swiss National Science Foundation (SNSF) under the Joint Research Projects (JRPs) program, and by the Japan Science and Technology (JST) through the Strategic International Collaborative Research Program (SICORP). References Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, Robust anion conductive polymers containing perfluoroalkylene and pendant ammonium groups for high performance fuel cells, J. Mater. Chem. A 5 (2017) 24804–24812, https://doi.org/10.1039/c7ta09409d.Otsuji, Naoki Yokota, D. A. Tryk, K. Kakinuma, K. Miyatake, M. Uchida, Performance hysteresis phenomena of anion exchange membrane fuel cells using an Fe–N–C cathode catalyst and an in-house developed polymer electrolyte, Journal of Power Sources, 487 (2021) 229407, https://doi.org/10.1016/j.jpowsour.2020.229407 Figure 1

Effects of Native Solid Electrolyte Interphase Layer Formation of Cu Electrode on Lithium Electrodeposition/Dissolution Processes

Lithium has been extensively expected as one of the most ideal anode materials of the next generation lithium-based batteries such as a lithium-air battery (LAB), because of its higher theoretical specific capacity (3860 mA h g-1) and its most negative redox potential (-3.04 V vs. SHE). During charging, however, it is well known that the dendrite, which further leads to poor performance and short circuit, forms on the lithium anode surface. In addition, solid electrolyte interphase (SEI), which is generated by decomposition of electrolytes and/or solvents, also accumulates on the anode surface during the anode reaction. An ideal SEI layer is expected to be higher and lower conductive for lithium ion and electron, respectively, and it is flexible and has a relatively uniform flat surface with an appropriate thickness, in order to avoid dendrite formation [1]. Thus, we have been trying to construct the “ideal SEI” on the electrode surface [2]. During the electrochemical reaction, on the other hand, electrochemical quartz crystal microbalance (EQCM) technique gives us information not only of mass change on the electrode surface but also resonance resistance change, which shows surface area change of the electrode [3,4] and/or density and viscosity change at the electrode/electrolyte solution interface [5,6]. Moreover, this technique provides us the viscoelasticity of the formed layers on the electrode by the admittance analysis. Using this technique, we found that the native-SEI, which is prepared by the pre-electrochemical treatment of Cu EQCM electrode, strongly effects on the lithium electrodeposition/dissolution processes. Acknowledgements: This work was totally supported by the Advanced Low Carbon Technology Research and Development Program (ALCA), specially promoted research for innovative next generation batteries (SPRING) from the Japan Science and Technology (JST).

Effective Pre-Electrochemical Treatment of Cu EQCM Electrode on Lithium Electrodeposition/Dissolution Processes

Lithium has been extensively expected as one of the most ideal anode materials of the next generation lithium-based batteries, because of its higher theoretical specific capacity (3860 mA h g-1) and its most negative redox potential (-3.04 V vs. SHE). On the lithium anode surface, however, it is well-known that the dendrite, which further leads to poor battery performance and short circuit, forms in charging. In addition, solid electrolyte interphase (SEI), which is generated by decomposition of electrolytes and/or solvents, also accumulates on the anode surface during the anode reaction. An ideal SEI layer is expected to be higher and lower conductive for lithium ion and electron, respectively, and it is flexible and has a relatively uniform flat surface with an appropriate thickness, in order to avoid dendrite formation [1]. During the electrochemical reaction, on the other hand, electrochemical quartz crystal microbalance (EQCM) technique gives us information not only of mass change on the electrode surface but also resonance resistance change, which shows surface area change of the electrode [2,3] and/or density and viscosity change at the electrode/electrolyte solution interface [4,5]. Using this technique, we found that the pre-electrochemical treatment of the Cu EQCM electrode strongly effects on the lithium electrodeposition/dissolution processes. Acknowledgements: This work was totally supported by the Advanced Low Carbon Technology Research and Development Program (ALCA), specially promoted research for innovative next generation batteries (SPRING) from the Japan Science and Technology (JST).

Pre-Electrochemical Treatment Effect of Cu Eqcm Electrode on Lithium Electrodeposition/Dissolution Processes

Lithium has been extensively expected as one of the most ideal anode materials of the next generation lithium-based batteries, because of its higher theoretical specific capacity (3860 mA h g-1) and its most negative redox potential (-3.04 V vs. SHE). On the lithium anode surface, however, it is well known that the dendrite, which further leads to poor performance and short circuit, forms. In addition, solid electrolyte interphase (SEI), which is generated by decomposition of electrolytes and/or solvents, also accumulates on the anode surface during the anode reaction. An ideal SEI layer is expected to be higher and lower conductive for lithium ion and electron, respectively, and it is flexible and has a relatively uniform flat surface with an appropriate thickness, in order to avoid dendrite formation [1]. During the electrochemical reaction, on the other hand, electrochemical quartz crystal microbalance (EQCM) technique gives us information not only of mass change on the electrode surface but also resonance resistance change, which shows surface area change of the electrode [2,3] and/or density and viscosity change at the electrode/electrolyte solution interface [4,5]. Using this technique, we found that the pre-electrochemical treatment of Cu EQCM electrode strongly effects on the lithium electrodeposition/dissolution processes. Acknowledgements This work was totally supported by the Advanced Low Carbon Technology Research and Development Program (ALCA), specially promoted research for innovative next generation batteries (SPRING) from the Japan Science and Technology (JST).

Special Issue on Enhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines

Special Issue on Enhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines

Overview of ERATO Minato Project: The Art of Discrete Structure Manipulation between Science and Engineering

Discrete structure manipulation is a fundamental technique for solving many kinds of problems. Recently, BDD (Binary Decision Diagram) and ZDD (Zero-suppressed BDD) attract a great deal of attention, because they efficiently represent and manipulate large-scale combinational logic data, which are the basic discrete structures in various fields of applications, including system verification/optimization, knowledge discovery, statistical analysis, etc. Last year, the author proposed a new research project to focus on BDDs/ZDDs. In this proposal, as a new viewpoint of BDD/ZDD-based techniques, we intended to organize an integrated method of algebraic operations for manipulating various types of discrete structures, and to construct standard techniques for efficiently solving large-scale and practical problems. Fortunately, the proposal was accepted by JST (Japan Science and Technology Agency) as an ERATO (Exploratory Research for Advanced Technology) project, one of the prestigious projects in Japan. In this article, we present an overview of our research project. Our project aims to develop “The Art” of discrete structure manipulation between Science and Engineering.

Construction of Development Technology of Next Generation Applied Electromagnetic Machinery in Japan

The national project of the development technology of next generation applied electromagnetic machinery was founded in Oita as Oita Prefecture Innovative JST (Japan Science and Technology Agency) Research Program. In this paper, outline of this project is introduced and the basic technology which is based on vector magnetic property is described. Especially the vector magnetic properties in high flux density level of 1.9 T are shown. As the example results, the dynamic vector magnetic characteristic is applied to the surface permanent magnet motor.

Vector magnetic property for development of high density machines

The national project of the development technology of next generation applied electromagnetic machinery was founded in Oita as Oita Prefecture Innovative JST (Japan Science and Technology Agency) Research Program. In this paper, outline of this project is introduced and the basic technolo gy which is based on vector magnetic property is described. Especially the vector magnetic properties in high flux density level of 1 .9 T are shown. As the example results, the dynamic vector magnetic characteristic is applied to the surface permanent magnet motor.

LASER PULSE CIRCULATION SYSTEM FOR COMPACT MONOCHROMATIC TUNABLE HARD X-RAY SOURCE

We are construcing a laser electron Compton scattering monochromatic tunable hard X-ray source. It consists of the X-band (11.424 GHz) electron linear accelerator and Q-switch Nd : YAG laser. This work is a part of the JST (Japan Science and Technology Agency) project. The whole system is a part of the national project on the advanced compact medical accelerator development, hosted by NIRS (National Institute for Radiological Science). The University of Tokyo and KEK are working for the X-ray source. Main advantage of this X-ray source is monochromatic tunable hard X-rays (10-50keV) with the intensities of 108-109 photons/s. The table-top size X-ray source can generate dual energy monochromatic hard X-ray by turns and it takes about 40ms to chage the X-ray energy. It is calculated that the X-ray intensity is 107 photons/RF-pulse (108 photons/s in 10 pps) by the 35MeV electron and YAG laser (2J/pulse). The X-band beam line for the demonstration is under construction. We designed a laser pulse circulation system to increase the X-ray yield 10 times higer (up to 108 photons/RF-pulse, 109 photons/s). It can be proved that the laser total energy increases 10 times higher by the principle experiment with the lower energy laser (25mJ/pulse).

Theoretical Simulations of Scanning Probe Microscopy for Organic and Inorganic Materials

Current topics are introduced from the results for the JST (Japan Science and Technology Agency) project for the development of the theoretical simulator of scanning probe microscopy. In spite of the crucial role played by the theoretical simulation for understanding experimental results, the theoretical calculations so far tried have been computationally very demanding. Thus one of the aim of this project is the development of efficient methods for the simulation of STM(Scanning Tunneling Microscopy), AFM(Atomic Force Microscopy) and KFM(Kelvin Force Microscopy) and their spectroscopy. Toward this purpose the simplified and efficient calculation program, as well as user friendly GUI tools for the wide range users are aimed in the JST SPM project. Another targets of the project are the development of a new frontier of the SPM simulation, in particular, for supporting experiments on biological and organic molecular systems, and for the measurement in liquids. We will discuss for the STM simulation the inelastic tunneling processes and decorated tip model. As for the AFM, we consider how to treat the dynamic cantilever motion in liquids, and the theoretical simulation for some of the protein molecules. Keywords: Kelvin Force Microscopy (KFM), Scanning Tunneling Microscopy (STM), BCA II Molecule, Green fluorescent protein (GFP), AFM simulation

Two-colored Laser Circulation System for Monochromatic Tunable Hard X-ray Source

A two-colored laser pulse circulation system for a monochromatic tunable hard X-ray source via laser electron Compton scattering is investigated. The demonstration system of the X-ray source is under construction at the University of Tokyo. It consists of the X-band (11.424 GHz) electron linear accelerator and two Nd: YAG laser systems. The main advantage of this system is a monochromatic tunable hard X-ray. It is calculated that the X-ray intensity will be about 108 photons/s. In order to enhance the X-ray intensity for medical applications such as dual energy X-ray CT, a two-colored laser pulse circulation system has been designed. The laser pulse circulation experiment without an electron beam has been carried out by using a Nd: YAG laser fundamental wave (50 mJ) and a second harmonics wave (25 mJ). The result shows that the X-ray intensity can be enhanced by a factor of 10 times higher (i.e., up to 109 photons/s). This work is a part of the JST (Japan Science and Technology Agency) project. The entire X-ray source system is a part of a larger national project on the development of an advanced compact medical accelerator sponsored by the NIRS (National Institute for Radiological Science). The University of Tokyo and KEK are responsible for the X-ray source.

Two-colored Laser Circulation System for Monochromatic Tunable Hard X-ray Source

A two-colored laser pulse circulation system for a monochromatic tunable hard X-ray source via laser electron Compton scattering is investigated. The demonstration system of the X-ray source is under construction at the University of Tokyo. It consists of the X-band (11.424 GHz) electron linear accelerator and two Nd: YAG laser systems. The main advantage of this system is a monochromatic tunable hard X-ray. It is calculated that the X-ray intensity will be about 108 photons/s. In order to enhance the X-ray intensity for medical applications such as dual energy X-ray CT, a two-colored laser pulse circulation system has been designed. The laser pulse circulation experiment without an electron beam has been carried out by using a Nd: YAG laser fundamental wave (50 mJ) and a second harmonics wave (25 mJ). The result shows that the X-ray intensity can be enhanced by a factor of 10 times higher (i.e., up to 109 photons/s). This work is a part of the JST (Japan Science and Technology Agency) project. The entire X-ray source system is a part of a larger national project on the development of an advanced compact medical accelerator sponsored by the NIRS (National Institute for Radiological Science). The University of Tokyo and KEK are responsible for the X-ray source.

Gene Classification Method Based on Batch-Learning SOM

1 Department of Electrical Information Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan 2 Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan 3 Department of Population Genetics, National Institute of Genetics, and the Graduate University for Advanced Studies, Mishima, Shizuoka, 441-8540, Japan 4 CREST, JST (Japan Science and Technology) 5 Research and Education Center for Genetic Information, Nara Institute of Science and Technology,8916-5 Takayama, Ikoma, Nara 630-0101, Japan 6 Department of Informatics and Mathematical Science, Gradute School of Engineering Science Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

Gene Classification by Self-Organization Mapping of Codon Usage in Bacteria with Completely Sequenced Genome

a95550@eie.yz.yamagata-u.ac.jp carlos@translell.eco.tut.ac.jp tikemura@ddbj.nig.ac.jp 1 Department of Electrical Information Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan 2 Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan 3 Department of Population Genetics, National Institute of Genetics, and the Graduate University for Advanced Studies, Mishima, Shizuoka, 441-8540, Japan. 4 Department of Developmental Genetics, National Institute of Genetics 5 CREST, JST (Japan Science and Technology)