▎ 摘　　要

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. (C) 2015 Elsevier Ltd. All rights reserved.