Comparative Investigation of Performance Degradation in Fuel Cell Membrane Electrodes during Long-Term Aging

Long-term operational stability is critical for the practical deployment and commercialization of proton-exchange membrane fuel cells (PEMFCs). However, membrane electrode assemblies (MEAs) in fuel cells exhibit significant performance degradation and accelerated decay after aging. This behavior arises from multiple coupled degradation mechanisms that remain not yet fully understood. Here, we employ confocal Raman mapping to investigate degradation mechanisms in a Pt/C catalyst layer (CL) characterized by a heterogeneous graphitization gradient. In particular, comparison of the fresh and aged samples (0 and 5000 h aging) shows that electrochemical performance degradation (approximately 40% loss in electrochemically surface area (ECSA)) is accompanied by the spatial redistribution and reorganization of carbon structural features. This reorganization may alter the interfacial response of the CL. Spatial Raman fingerprints further reveal anisotropic distributions of defect-related features within the CL. Together with electrochemical measurements, these findings mechanistically connect structural changes to electrochemical degradation in Pt/C MEA, providing a multiscale perspective on their interplay during long-term operation.