Electrochemical Indicators for Designing Durable Low-Pt Fuel Cell Catalysts

Improving the durability of platinum (Pt)-based catalysts for the oxygen reduction reaction (ORR) remains a central challenge in the commercialization of proton exchange membrane fuel cells (PEMFCs), yet simple and effective indicators to guide the rational design of highly stable Pt-based catalysts are still lacking. Herein, we identify initial electrochemically active surface area (ECSA) and dry proton accessibility (DPA) as two key indicators for unraveling cathodic Pt/C catalyst degradation. Systematic studies on a library of Pt/C catalysts with a wide range of initial ECSA (49-114 m² g_Pt ^-1) and DPA (27%-91%) reveal clear relationships between these two indicators and ECSA loss: at a comparable DPA, ECSA loss decreases significantly with the reduction in initial ECSA; at a similar initial ECSA, lower DPA effectively mitigates ECSA loss; and the influence of DPA on ECSA loss becomes increasingly prominent as initial ECSA decreases. Regression analysis further clarifies the respective roles of these two indicators: initial ECSA is the dominant factor associated with ECSA loss within the catalyst library, while DPA further modulates degradation depending on the initial ECSA level. These findings suggest that catalyst durability can be improved by prioritizing the reduction of initial ECSA, with further benefits achieved by lowering DPA.