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

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 sluggish kinetics of the oxygen reduction/oxygen evolution reactions (ORR/OER), limiting the commercialization possibilities. Herein, a new type of oxygen vacancies enriched Co-doped molybdenum (oxy)nitride quantum dots anchored nitrogen-doped carbon nanosheets (VO-CMON@NCNs) was demonstrated as an advanced air-cathode for rechargeable ZABs. Such VO-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 optimal VO-CMON@NCN-800 air-cathode showed an ultrahigh specific capacity of 721.2 mAh gzn−1 at a current density of 5 mA cm2, a tremendous peak power density of 143.7 mW cm2, and an ultralong cycling life for 500 h. These consequences suggest that the oxygen vacancies enriched VO-CMON@NCN can be served as promising bifunctional catalysts for next-generation metal-air batteries and other energy-related applications.