(Invited) Catalyst Challenges for Ion-Pair High Temperature Proton Exchange Membrane Fuel Cells

Abstract

High temperature proton exchange membrane fuel cells (HT-PEMFCs) have several merits over low temperature PEMFCs, including simplified fuel cell systems and high CO tolerance. Recently developed ion-pair HT-PEMFCs1 has a significantly lower concentration of phosphoric acids in the membrane-electrode assembly (MEA) that allows ion-conducting binders (ionomers) in the electrodes. Here, we first explain the difference in MEA configurations and fuel cell performance between conventional polybenzimidazole-based and ion-pair HT-PEMFCs2. Next, we discuss catalyst challenges for ion-pair HT-PEMFCs by comparing half-cell and single-cell results.We focus on three critical areas in that electrocatalysts face challenges: i) phosphate anion poisoning on oxygen reduction reaction catalysts, ii) phenyl adsorption on hydrogen oxidation reaction catalysts and iii) phosphoric acid flooding. Research progress mitigating those adverse effects is demonstrated using various commercial Pt-based catalysts and homemade ionomers. Lastly, we provide general directions for designing high-performing catalysts of ion-pair HT-PEMFCs.References Lee, K. S.; Spendelow, J. S.; Choe, Y. K. Fujimoto, C.; Kim, Y. S. An Operationally Flexible Fuel Cell Based on Quaternary Ammonium-Biphosphate Ion Pairs, Nature Energy, 1, 16120 (2016).Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells, Nature Energy, 7, 248 (2022).