Disentangling the Multiscale Degradation Pathways in Fe–N–C Fuel Cells With Advanced Characterization Techniques

ABSTRACT Proton exchange membrane fuel cells hold immense potential for sustainable hydrogen energy utilization but face commercialization barriers due to reliance on costly platinum‐group‐metal (PGM) catalysts. Among PGM‐free alternatives, Fe‒N‒C catalysts have emerged as leading candidates due to their high oxygen reduction reaction activity; however, they suffer from rapid performance decay during initial operation. Understanding the degradation mechanisms of Fe‒N‒C catalysts is crucial for improving their stability and enabling their commercialization. Major degradation pathways include the demetalation of active sites, oxidation of carbon support, and collapse of triple‐phase boundaries. However, these pathways’ driving forces, temporal sequences, and relative contributions under varying operating conditions remain unclear. This review synthesizes pioneering studies elucidating the multiscale degradation pathways in Fe‒N‒C fuel cells, emphasizing the role of advanced characterization techniques in disentangling mechanistic complexities. By correlating structural evolution timelines with impacts of intrinsic structures and operational parameters, we establish a framework to guide targeted stabilization strategies, helping to address critical knowledge gaps toward durable Fe–N–C fuel cells.