Nitrogen/sulfur dual-doped 3D reduced graphene oxide networks-supported CoFe2O4 with enhanced electrocatalytic activities for oxygen reduction and evolution reactions

To expedite the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in electrochemical systems, efficient nonprecious electrocatalysts are highly desired. In this work, a hybrid of CoFe2O4 nanoparticles supported on nitrogen/sulfur dual-doped three-dimensional (3D) reduced graphene oxide networks (CFO/NS-rGO) has been designed and fabricated. The doping of N and S provide the graphene networks with a large amount of defects. Moreover, both N and S doped in reduced graphene oxide play important roles in engineering the covalent coupling between CoFe2O4 and the 3D graphene networks. The covalent coupling between CoFe2O4 and NS-rGO along with the hierarchical porous structure and 3D networks endow the hybrid with a pronounced ORR activity (4-electron pathway), superior OER activity (comparable to that of the state-of-the-art RuO2/C catalyst) and high durability toward both ORR and OER.