Exploring Durable Single-Atom Catalysts for Proton Exchange Membrane Fuel Cells

Exploring low-cost, highly active, and durable oxygen reduction catalysts is essential for the widespread use of proton exchange membrane fuel cells. Fe−N−C catalysts with nitrogen-coordinated single-atom (Fe−N_x) active sites are the most promising candidates due to their highest activity in acid media among platinum-group-metal-free catalysts. However, the application of Fe−N−C catalysts in realistic fuel cells is still hindered by the conundrum of insufficient stability. This review focuses on the understanding of the structure−stability relationship of Fe−N−C catalysts, which provides valuable guidance for the rational material design toward improved stability. The most significant achievements in recent years are the discovery of several site-specific degradation mechanisms and the identification of intrinsically stable active sites. The development of Fe-free single-atom catalysts is also discussed as an alternative solution.