A 3D PtCo degradation model for long-term performance prediction of a scaled-up PEMFC under constant voltage operation

Abstract

The non-uniform distribution of reactants, pressure, temperature and reaction rate in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3 % after 80,000 h operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its non-uniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime.