Abstract
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•Co/CoSe heterojunctions were constructed as bifunctional electrocatalysts via partial reduction.•The charge redistribution is revealed by systematic characterizations and DFT calculations.•Both ORR and OER activities are promoted due to the Mott-Schottky effect of Co/CoSe heterojunction.•The Co/CoSe-based Zn-air battery delivers high energy output and excellent cyclability.
Design of low-cost and high-performance bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key topic in the development of zinc-air batteries. In this work, a facile in-situ partial reduction strategy is proposed to fabricate Co/CoSe Schottky junctions encapsulated in carbon (Co/CoSe@NC). The heterojunction in the Co/CoSe@NC can tune Fermi level and charge redistribution to accelerate the charge transfer, while the metal–organic framework derived skeleton provides well-defined structure and abundant mesopores to facilitate mass transport. The accelerated charge transfer through the Mott-Schottky heterostructure can improve the intrinsic electrocatalytic activities for both electron-gaining ORR and electron-losing OER, which are confirmed by systematic characterizations and density functional theory calculations. Furthermore, the Zn-air battery with the as-prepared Co/CoSe@NC heterojunction shows better performance than the Pt/RuO2-based counterpart, demonstrating good feasibility for practical applications.