Atomically dispersed Fe/Co-N-C and their composites for proton exchange membrane fuel cells

Seeking cheaper catalysts to replace Pt-based materials for the oxygen reduction reaction (ORR) has always been a key objective in developing green electrochemical energy devices such as fuel cells. Burgeoning atomic Fe/Co-N-C and their composite catalysts are undoubtedly the most promising candidates owing to their low cost, excellent electrical conductivity, high chemical stability, and tunable electronic and geometric structures through nanoengineering strategies. Thus, exploiting efficient Fe/Co-N-C and their composite catalysts is crucial; however, conducting such research poses critical challenges. Herein, recent developments in Fe/Co-N-C and their composite catalysts for the ORR are systematically reviewed, mainly focusing on their applications in proton exchange membrane fuel cells (PEMFCs). Different preparation methods and characterization techniques for atomic Fe/Co sites are summarized, and insights into mechanisms of the ORR on these sites are discussed. Strategies to enhance the activities of Fe/Co-N-C and their composite catalysts are emphasized, along with the corresponding performance of PEMFCs. Finally, prospects for the rational design and future development for practical applications of Fe/Co-N-C and their composite catalysts are presented. Atomically dispersed Fe/Co-N-C and their composites for fuel cells.