Engineering asymmetric Fe coordination centers with hydroxyl adsorption for efficient and durable oxygen reduction catalysis

Single-atom Fe catalysts are a promising substitute to Pt catalysts for oxygen reduction reaction (ORR). Adjusting metal energy level through direct atomic interface regulation can effectively improve catalytic performance but still in its infancy. Herein, highly active nitrogen and sulfur dual-coordinated asymmetric Fe center anchored in carbon nanoparticles were developed. Spontaneously absorbed OH ligand is steadily anchored in asymmetric atomic interface, constructing new FeN 3 S-OH moiety. Theoretical calculations reveal that the incorporated S atom combined with OH ligand as energy level modifier effectively activate Fe center by electronic modulation and d -band center shift, rendering improved ORR activity of FeNSC-2Fe with E 1/2 of 0.913 V in alkaline, 0.806 V in acidic and 0.711 V in neutral media. The FeNSC-2Fe-based device displays high power density of 306 mW cm −2 in Zn-air battery and 2485 mW m −2 in microbial fuel cell. This work provides a new perspective for the controllable synthesis and performance optimization for electrocatalysts. • Adjusting metal energy level through direct atomic interface regulation. • Single-atom iron catalysts with asymmetric FeN3S-OH structure in carbon matrix. • Introduced S atom and OH ligand jointly boost the oxygen reduction reactivity. • Microbial fuel cell and Zn-air battery with high power density and good stability.