Cobalt-doped Mn3O4 nanocrystals embedded in graphene nanosheets as a high-performance bifunctional oxygen electrocatalyst for rechargeable Zn–Air batteries

A non-noble-metal bifunctional catalyst with efficient and durable activity towards both the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)is crucial to the development of rechargeable Zn-air batteries.Herein,a facile one-step hydrothermal method is reported for the synthesis of a high-performance bifunctional oxygen electrocatalyst,cobalt-doped Mn_(3)O_(4) nanocrystals supported on graphene nanosheets(Co–Mn_(3)O_(4)/G).Compare to pristine Mn_(3)O_(4),this Co–Mn_(3)O_(4)/G exhibits greatly enhanced electrocatalytic activity,delivering a halfwave potential of 0.866 V for the ORR and a low overpotential of 275 mV at 10 mA cm^(-2) for the OER.The zinc-air battery built with Co–Mn_(3)O_(4)/G shows a reduced charge–discharge voltage of 0.91 V at 10 mA cm^(-2),an power density of 115.24 mW cm^(-2) and excellent stability without any degradation after 945 cycles(315 h),outperforming the state-of-the-art Pt/C–Ir/C catalyst-based device.