A multi-field numerical study of freeze-induced interfacial damage in PEMFC catalyst layers during cold start

Cold start-up at sub-zero temperatures remains one of the primary challenges to the durability of proton exchange membrane fuel cells (PEMFCs). This study proposes a multi-field coupled interfacial damage model that accounts for freezing-induced stresses, successfully captures the coupled effects between ice formation and interfacial stress evolution under cyclic cold-start conditions. The mechanical degradation and microstructural evolution of the CL during cold-start operations were systematically investigated under varying loading conditions. The results indicate that cyclic temperature and humidity variations are the primary drivers of interfacial crack initiation: compared with normal-temperature startup conditions, low-temperature cold start leads to 79.3% and 57.5% increases in the maximum interfacial separation ( S ) and the ratio of crack length to interface length ( L ), respectively, driven by the amplified cyclic variations in temperature and humidity. Freezing-induced stress further acts as a critical accelerating factor, increasing S and L by an additional 36.6% and 14.3% in the first cold-start cycle, whereas this effect gradually weakens in subsequent cycles.