The manipulation of Ni/MnO heterostructures within carbon hierarchical superstructures as bifunctional oxygen electrocatalysts for enhanced Zn–air batteries

Abstract

Rational developing high-performance and economically efficient dual-functional oxygen electrocatalysts to drive the lumberly reactivity rates of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn–air batteries is highly attractive, yet remains conceptually challenging. Herein, Ni/MnO heterostructure nanosheets and nanoparticles firmly anchored onto the N-doped carbon nanofibers (noted as Ni/MnO@N-C NS/NFs) for efficient bifunctional ORR/OER electrocatalysis are designed and realized through a facile electrospinning–pyrolysis–etching strategy. The epitaxial in situ grown Ni/MnO with enriched oxygen vacancies stimulated the charge redistribution in their coupling regions, which effectively optimizes the adsorption/desorption of O-related intermediates in ORR/OER. Benefiting from the Ni/MnO heterostructure moieties and the unique two-dimensional/one-dimensional (2D/1D) superstructure of carbon support with abundantly dispersive active species, the resultant Ni/MnO@N-C NS/NFs deliver robust ORR activity and OER property (an overpotential of 306 mV to obtain 10 mA·cm⁻²) with a smaller potential gap (ΔE = 0.77 V) in alkaline electrolyte. More significantly, practical zinc–air battery building with Ni/MnO@N-C NS/NFs delivers a higher open circuit voltage, excellent output power density, and prominent durability with stable charging and discharging cycle life. The present work demonstrates a crucial understanding of building advanced heterostructure electrocatalysts with enriched oxygen vacancies for metal-air batteries application.