Engineering of heterointerface of ultrathin carbon nanosheet-supported CoN/MnO enhances oxygen electrocatalysis for rechargeable Zn–air batteries

The elaborately constructed CoN/MnO heterojunction immobilized onto ultrathin N-doped carbon nanosheets as an excellent bifunctional electrocatalyst for Zn-air batteries. [Display omitted] •The fabrication of abundant CoN/MnO heterointerfaces is achieved in ultrathin carbon nanosheets.•The CoN/MnO@NC exhibits high bifunctional activities with an extremely small potential gap of 0.69 V between OER and ORR.•The application of CoN/MnO@NC as an excellent air cathode is demonstrated by both liquid and flexible quasi-solid-state rechargeable Zn-air batteries.•The CoN/MnO heterointerfaces optimize chemisorption energies for reaction intermediates and accelerate reaction kinetics. Designing bifunctional electrocatalysts with outstanding reactivity and durability towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has remained a long-term aim for metal-air batteries. Achieving the high level of fusion between two distinct metal components to form bifunctional catalysts with optimized heterointerfaces and well-defined morphology holds noteworthy implications in the enhancement of electrocatalytic activity yet challenging. Herein, the fabrication of numerous heterointerfaces of CoN/MnO is successfully realized within ultrathin carbon nanosheets via a feasible self-templating synthesis strategy. Experimental results and theoretic calculations verify that the interfacial electron transfer from CoN to MnO at the heterointerface engenders an ameliorated charge transfer velocity, finely tuned energy barriers concerning reaction intermediates and ultimately accelerated reaction kinetics. The as-prepared CoN/MnO@NC demonstrates exceptional bifunctional catalytic performance, excelling in both OER and ORR showcasing a low reversible overpotential of 0.69 V. Furthermore, rechargeable liquid and quasi-solid-state flexible Zn-air batteries employing CoN/MnO@NC as the air-cathode deliver remarkable endurance and elevated power density, registering values of 153 and 116 mW cm−2 respectively and exceeding Pt/C + RuO2 counterparts and those reported in literature. Deeply exploring the effect of electron-accumulated heterointerfaces on catalytic activity would contribute wisdom to the development of bifunctional electrocatalysts for rechargeable metal-air batteries.