Recent advances in Fe–N–C-and Co–N–C-based materials as bifunctional electrocatalysts for oxygen reduction and oxygen evolution

Fe–nitrogen–carbon(Fe–N–C)-and Co–nitrogen–carbon(Co–N–C)-based electrocatalysts have been widely concerned because of their high OER/ORR activity, low metal cost, and simple preparation. The exploration of Fe–N–C and Co–N–C single atombased catalysts with high activity and stability to overcome the slow kinetics of oxygen reduction and oxygen evolution reactions is also the key to the development of efficient electrolytic water, fuel cells, and rechargeable metal–air batteries. Fe–N–C and Co–N–C single atom-based electrocatalysts have the advantages of a high utilization rate of metal atoms and high electrocatalytic activity, and are ideal catalysts for promoting electrochemical energy conversion and storage. The general principles of designing Fe–N–C and Co–N–C single atom-based electrocatalysts are reviewed in this paper. Then, the strategies to improve the bifunctional catalytic activity and stability are proposed. Finally, the challenges and prospects of Fe–N–C and Co–N–C single atom-based catalysts are well summarized. This review will provide a reference for the directed optimization of Fe–N–C and Co–N–C single atom-based catalysts.