Degradation of core-shell Pt3Co catalysts in proton exchange membrane fuel cells (PEMFCs) studied by mathematical modeling

Understanding the degradation process of Pt-based catalysts is a crucial step to improve the durability of PEMFCs. A mathematical model is established to study the electrochemical surface area (ECA) loss and structural/compositional evolutions of core-shell Pt3Co catalysts along the cathode under a certain circumstance. Three major processes are included in this model: Pt dissolution and re-precipitation on the Pt shell, Co leaching from the bulk and deposition of Pt ions in the membrane due to crossover hydrogen. The results show that the significant ECA loss next to the membrane is mainly attributed to the severe particle corrosion rather than variation of the particle size distribution. The Pt shell thickness and Pt/Co atomic ratio decrease from gas diffusion layer (GDL)/CCL interface to the cathode catalysts layer (CCL)/membrane interface, while the Co mass loss shows an inverse trend. This work demonstrates that mathematical modeling is effective to predict the structural and compositional evolutions of the catalyst particles across the CCL, and therefore is useful to evaluate the complete performance degradation of Pt3M catalysts for PEMFCs in the future.