Simulation of Performance Tradeoffs in Ceria Supported Polymer Electrolyte Fuel Cells

Abstract

Ceria-supported membrane electrode assemblies (MEAs) can effectively protect the membrane at open circuit voltage conditions; however, performance tradeoffs have been observed experimentally with the use of membrane additives. In the present work, a comprehensive, transient in situ membrane durability model for ceria-supported MEAs is developed and applied to investigate the fundamental mechanisms of the performance tradeoffs. The modeling results reveal that proton starvation may occur in the cathode catalyst layer due to local Ce3 + accumulation and associated reductions in proton conductivity and oxygen reduction kinetics. Significant performance tradeoffs in the form of combined ohmic and kinetic voltage losses are therefore evident and shown to increase with current density. Reduced ceria additive loading and increased cathode ionomer volume fraction are proposed as potential mitigation strategies to reduce the voltage losses caused by proton starvation. A lower initial Ce3 + concentration is demonstrated to reduce voltage losses without compromising membrane durability at high cell voltages. However, the harmful Fe2 + concentration in the membrane increases with the Ce3 + concentration, which suggests that ceria-supported MEAs can experience higher rates of degradation than baseline MEAs at low cell voltages. Strategic MEA design and optimization is recommended in order to ensure membrane durability at low cell voltages.