Novel cobalt-doped molybdenum oxynitride quantum dot@N-doped carbon nanosheets with abundant oxygen vacancies for long-life rechargeable zinc–air batteries

Abstract

Rechargeable zinc–air batteries (ZABs) have emerged as promising alternatives for conventional Li-ion batteries due to their high energy density and low manufacturing cost. However, Pt/C and RuO₂-based conventional rechargeable ZABs are mainly constrained by the sluggish kinetics of oxygen reduction/oxygen evolution reactions (ORR/OER), limiting commercialization possibilities. Herein, a new type of oxygen vacancies enriched cobalt-doped molybdenum oxynitride quantum dot-anchored N-doped carbon nanosheets (V_O-CMON@NCNs) was demonstrated as an advanced air-cathode for long-life rechargeable ZABs. Such V_O-CMON@NCN catalyst has an exceptional ORR performance with a high half-wave potential of 0.857 V and tremendous OER performance with an ultrasmall overpotential of 240 mV at a current density of 10 mA cm⁻², outperforming conventional Pt/C and RuO₂ catalysts. As proof of concept, rechargeable ZABs with an optimal V_O-CMON@NCN-800 air-cathode showed an ultrahigh specific capacity of 721.2 mA h g_Zn⁻¹ at a current density of 5 mA cm⁻², a tremendous peak power density of 143.7 mW cm⁻², and ultralong cycling life of 500 h. These consequences suggest that the oxygen vacancies enriched V_O-CMON@NCN can serve as promising bifunctional catalysts for next-generation metal–air batteries and other energy-related applications.