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

Abstract

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