Dominating Role of Interfacial N–Ni Coordination in Spinel Nickel Ferrite/N‐Doped Graphene Hybrids for Boosting Reversible Oxygen Electrocatalysis

Abstract

Designing efficient and affordable electrocatalysts for reversible oxygen electrocatalysis (oxygen reduction reaction [ORR] and oxygen evolution reaction [OER]) reactions is highly desirable for rechargeable metal–air batteries. The hybrid electrocatalysts composed of transition metal oxides and N‐doped carbonaceous materials are promising bifunctional ORR/OER electrocatalysts, whose improved electrocatalytic activities can be attributed to the synergistic effect originated from the metal–N–C active sites. Herein, NiFe2O4/N‐doped graphene (NFO/NG) composites are prepared which own enhanced OER, especially superior ORR performance for the utilization of rechargeable Zn–air batteries. Significantly, it is also verified that the interfacial Ni–(pyridinic or pyrrolic) N–C species, rather than Fe–N–C, play key role infactors for promoting ORR/OER bifunctional electrocatalysis. The optimized catalyst displays remarkably reduced overpotential for both ORR and OER with an overall potential difference as low as 0.67 V. The assembled rechargeable Zn–air battery shows a high specific capacity (513.6 mA h gzn−1) and power density (173.6 mW cm−2), as well as a long‐term cycling stability.

Keywords

• bifunctional electrocatalysts
• nitrogen-doped graphene
• spinel oxides
• synergistic effects
• zinc–air batteries