A Review of Coupled Degradation Mechanisms in PEMFCs: Thermal Management, Hydrogen Crossover and Mitigation Strategies

Proton exchange membrane fuel cells (PEMFCs) offer high efficiency and zero emissions, but durability remains a major barrier to commercialization. Degradation arises from coupled thermal, mechanical, and chemical stresses, yet these processes are often studied in isolation, reducing the accuracy of lifetime prediction. This paper systematically reviews PEMFC degradation, focusing on the coupling between thermal management failure and hydrogen crossover. Most importantly, it identifies a self-reinforcing thermal–hydrogen feedback in which localized overheating and permeated-hydrogen oxidation mutually amplify membrane defect propagation. Mitigation strategies spanning temperature control, hydrogen crossover suppression, intelligent prediction, and current challenges are then discussed. Mechanistically, thermal mismanagement promotes localized hot spots, while elevated temperature increases hydrogen diffusivity and accelerates defect growth, thereby sharply increasing crossover flux. Permeated hydrogen can be catalytically oxidized near defect sites, releasing additional heat and intensifying local membrane damage. Because the two stressors are coupled rather than independent, single-factor mitigation is insufficient; temperature control and hydrogen crossover suppression must be co-optimized. Future progress requires multiscale frameworks across scales, in situ multiphysics characterization, and artificial intelligence (AI)-driven control, moving from mechanistic understanding to engineering application.