Molten-salt confined synthesis of nitrogen-doped carbon nanosheets supported Co3O4 nanoparticles as a superior oxygen electrocatalyst for rechargeable Zn-air battery

Rational design and preparation of high-efficiency oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts is crucial for the large-scale practical application of rechargeable Zn-air batteries. In this work, employing a combined strategy of self-sacrificial template and molten-salt confinement effect, a facile one-step pyrolysis route has been developed to synthesize defect-rich N-doped carbon nanosheets supported Co3O4 nanoparticles (Co3O4@NCNs). The pyrolytic precursor is built up of NaCl encapsulated ZnO@zeolitic imidazolate framework-67 core-shell particles. Thanks to the pore-forming and oxygen source functions of ZnO and the confinement effect of NaCl, the holed NCNs in Co3O4@NCNs are interconnected into a 3D porous carbon structure with a high N-dopant level. The as-prepared Co3O4@NCNs catalyst exhibits excellent bifunctional ORR/OER electrocatalytic activities with a half-wave ORR potential (E1/2) of 0.84 V, an ultralow gap of 0.63 V between OER Ej = 10 mA/cm2 and ORR E1/2 potentials, and prominent long-term durability. Its rechargeable Zn-air battery displays a high power density up to 173.8 mW cm−2 and superior cycling stability. This work highlights a novel strategy for the component and architecture design of high-performance carbon-based electrocatalysts in energy conversion and storage systems. [Display omitted] •In-situ grown ZnO@ZIF-67 core-shell was constructed as precursor.•Molten-salt confinement effects led to holed N-doped carbon nanosheets supported Co3O4 NPs.•Co3O4@NCNs exhibits an excellent bifunctional activities with an ultralow ΔE = 0.63 V.•The battery has a peak power density of 165.8 mW cm−2and a capacity of 804 mAh g−1.