NiCo2O4 ultrathin nanosheets with oxygen vacancies as bifunctional electrocatalysts for Zn-air battery

Abstract

Economical, efficient and earth-abundant oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are highly required for Zn-air batteries, which is an attractive device for the next generation of energy storage. Herein, spinel-structured NiCo2O4 nanosheet with oxygen defects and ultrathin structure was developed as a bifunctional electrocatalyst for ORR and OER. The ultrathin thickness of NiCo2O4 nanosheets provided numerous active sites, and the oxygen vacancies improved the reactivity of the catalyst, thus leading to appropriate catalytic performance (an onset potential of 0.85 V for ORR and an onset overpotential of 340 mV for OER). Furthermore, the ultrathin NiCo2O4 nanosheets also showed superior activity for rechargeable Zn-air battery with the power density of 102.08 mW cm−2, which was comparable to the commercial Pt/C catalyst. The rational design in our study might be beneficial for the preparation of other high-performance bifunctional electrocatalysts.