Elucidating High-Potential Degradation Mechanisms in Proton Exchange Membrane Fuel Cells

High-potential states challenge proton exchange membrane fuel cell durability via carbon corrosion. However, the coupling between carbon corrosion and performance loss remains poorly understood. Here, a multiscale cathode catalyst layer (CCL) degradation model is developed, which integrates carbon corrosion, Pt degradation, and oxygen transport processes. Results reveal stage-dependent carbon corrosion and electrochemical active surface area (ECSA) loss, with nearly 20% of the carbon mass and over 40% of the ECSA lost in the first 100 cycles. The degradation rate then decelerates due to surface functional group transformation and corrosion-pathway shifts. Decomposition analysis after 2000 high-potential cycles attributes 66.8% of the ECSA loss to corrosion-induced Pt detachment. High-resolution characterization further reveals corrosion-driven ionomer redistribution and film thickening, raising the oxygen transport resistance of the ionomer film to 55.1% of the total. This work provides mechanistic insights into coupled degradation processes under high-potential conditions and offers guidance for durability-oriented CCL design.