Three-dimensional simulation of high temperature ion-pair PEM fuel cell integrated with agglomerate sub-model of cathode catalyst layer

A steady-state, isothermal simulation of a 3D high temperature (HT) ion-pair proton exchange membrane fuel cell (PEMFC) model, utilizing a quaternary ammonium biphosphate ion-pair membrane, was conducted in COMSOL Multiphysics for the first time. The performance of the fuel cell was analyzed, in terms of polarization curves, molar gas concentrations, and overpotential breakdown to determine mechanism resulting in loss. Experimental validation was performed for both non-protonated and protonated ion-pair fuel cells. The homogeneous catalyst layer model overestimated the performance at low catalyst loading by up to 32%. Hence, this study utilized an agglomerate sub-model of the cathode catalyst layer, to accurately capture the effect of catalyst loading on fuel cell performance. Additionally, a graded catalyst layer design was proposed to improve the catalyst utilization leading to high fuel cell performance. It was found that a graded catalyst layer with higher loading facing the membrane side improved the performance by 5.5% over uniformly loaded catalyst layer. Furthermore, the influence of operating conditions like temperature and back pressure is highlighted. Overall, this study offers a comprehensive approach to understanding HT ion-pair PEMFC operation and optimizing the catalyst structure.