Synthesis and Active Site Identification of Fe−N−C Single‐Atom Catalysts for the Oxygen Reduction Reaction

Abstract Fe−N−C catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) are still inferior to the Pt catalysts. The major downsides of Fe−N−C are the low density and ambiguous structural identification of active sites. Fe−N−C single‐atom catalysts (SACs) have shown great potential for maximizing the active site density and can serve as ideal platforms for investigating the nature of active sites. This review starts with a summary of the latest progress in the synthetic strategy for Fe−N−C SACs, followed by an introduction to the active site identification by atomic‐resolution techniques and electrochemical analyses. Finally, the major challenges are highlighted, and the prospective directions are proposed to guide the development of high‐performance Fe−N−C catalysts.