Heteroatom sulfur-doping in single-atom Fe-NC catalysts for durable oxygen reduction reaction in both alkaline and acidic media

Abstract

The need for highly efficient and economical Pt-free oxygen reduction reaction (ORR) electrocatalysts has led to the rapid development of single-atom transition metals anchored on heteroatom-doped carbon catalysts. However, their activity and stability remain below the requirements for practical applications. Herein, we propose a heteroatom (S)-doped hollow atomically dispersed Fe–N–C catalyst (H-S-Fe-NC) synthesized through a two-step thermal activation process. Compared with the un-doped Fe–N–C catalyst, the optimized H-S-Fe-NC catalysts display exceptional ORR activity and stability, achieving a high half-wave potential of 0.91 V in alkaline solution and 0.78 V in acidic solution, respectively. Combined experimental and theoretical results reveal the enhanced ORR activity of H-S-Fe-NC to be boosted by the introduction of S, which moderates the adsorption energy of the oxygen intermediates. Furthermore, we expand the application of the H-S-Fe-NC catalysts by using them in a zinc-air battery and proton-exchange membrane fuel cell.