▎ 摘　　要

Obtaining bifunctional electrocatalysts with high activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is a main hurdle in the application of rechargeable metal-air batteries. Earth-abundant 3d transition metal-based catalysts have been developed for the OER and ORR; however, most of these are based on oxides, whose insulating nature strongly restricts their catalytic performance. This study describes a metallic Ni-Fe nitride/nitrogen-doped graphene hybrid in which 2D Ni-Fe nitride nanoplates are strongly coupled with the graphene support. Electronic structure of the Ni-Fe nitride is changed by hybridizing with the nitrogen-doped graphene. The unique heterostructure of this hybrid catalyst results in very high OER activity with the lowest onset overpotential (150 mV) reported, and good ORR activity comparable to that for commercial Pt/C. The high activity and durability of this bifunctional catalyst are also confirmed in rechargeable zinc-air batteries that are stable for 180 cycles with an overall overpotential of only 0.77 V at 10 mA(-2).