Reduced Graphene Oxide‐Wrapped Co9–xFexS8/Co,Fe‐N‐C Composite as Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

Abstract Searching for highly efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) using nonnoble metal‐based catalysts is essential for the development of many energy conversion systems, including rechargeable fuel cells and metal–air batteries. Here, Co 9– x Fe x S 8 /Co,Fe‐N‐C hybrids wrapped by reduced graphene oxide (rGO) (abbreviated as S‐Co 9– x Fe x S 8 @rGO) are synthesized through a semivulcanization and calcination method using graphene oxide (GO) wrapped bimetallic zeolite imidazolate framework (ZIF) Co,Fe‐ZIF (CoFe‐ZIF@GO) as precursors. Benefiting from the synergistic effect of OER active CoFeS and ORR active Co,Fe‐N‐C in a single component, as well as high dispersity and enhanced conductivity derived from rGO coating and Fe‐doping, the obtained S‐Co 9– x Fe x S 8 @rGO‐10 catalyst shows an ultrasmall overpotential of ≈0.29 V at 10 mA cm −2 in OER and a half‐wave potential of 0.84 V in ORR, combining a superior oxygen electrode activity of ≈0.68 V in 0.1 m KOH.