Modeling of low-temperature fuel cell electrodes using non-precious metal catalysts

An electrode-scale, transport model for a proton-exchange-membrane fuel cell (PEMFC) cathode is presented. The model describes the performance of non-precious metal catalysts for the oxygen reduction reaction in a fuel cell context. Because of its relatively high thickness, emphasis is placed on phenomena occurring in the cathode layer. Water flooding is studied in terms of its impact on gas-phase transport and on electrochemically accessible surface area (ECSA). Although cathode performance in both air and oxygen are susceptible to ECSA loss, gas diffusion limitations at high current density in air are more significant. In oxygen, catalyst utilization at high current density is primarily limited by conductivity. For this reason, air fuel cell data is recommended over oxygen data for characterizing catalyst performance. Due to both ohmic and mass transport limitations, increased loading of low-cost catalysts does not necessarily lead to higher performance. Therefore, careful optimization of catalyst layer thickness is required.