▎ 摘　　要

We herein report a facile strategy to synthesize transition metal/spinel oxide nanoparticles coupled with nitrogen-doped graphene (Co/CoFe2O4@N-graphene) as an efficient bifunctional electrocatalyst toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This approach involves a spontaneous solution polymerization of polydopamine (PDA) film on graphene oxide (GO) sheets in the presence of Fe3+ and Co2+ to form the Fe/Co-PDA-GO precursor, followed by pyrolysis at 800 degrees C in argon (Ar) atmosphere. During the calcination process, Co/CoFe2O4 nanoparticles are in situ formed via high-temperature solid state reaction and are further entrapped by the PDA-derived N-doped carbon layer. As-prepared Co/CoFe2O4@N-graphene exhibits highly efficient catalytic activity and excellent stability for both ORR and OER in alkaline solution. This work reports a facile synthetic approach to develop highly active electrocatalysts while offering great flexibility to tailor their components and morphologies and thus provides a useful route to the design and synthesis of a broad variety of electrocatalysts.