Carbon-coated oxygen vacancies-rich Co3O4 nanoarrays grow on nickel foam as efficient bifunctional electrocatalysts for rechargeable zinc-air batteries

Abstract The bifunctional electrocatalyst has an important influence on the power output and cycle life of rechargeable zinc-air batteries. Cobalt oxides, especially Co3O4, have attracted much attention due to their high catalytic activity for oxygen evolution reaction (OER). It is difficult to improve the catalytic activity of oxygen reduction reaction (ORR) for rechargeable zinc-air batteries. In this paper, Co3O4 containing rich oxygen vacancies is prepared by in-situ growth on the nickel foam, and the carbon coating treatment on the surface increases the conductivity and stability of Co3O4, which prolongs its cycle life. The results show that moderate oxygen vacancies can achieve the best catalytic performance. The peak power density of zinc-air battery assembled by this air electrode can reach 54.5 mW cm−2, which is 51.4% higher than that of the untreated Co3O4 catalyst. The cycle life of the battery can reach 716 cycles (358 h), prolonging about 250 h compared with Co3O4 without carbon coating treatment. It is proved that the improved Co3O4 can increase the power output and cycle life of the rechargeable zinc-air battery, which helps to expand the application range of cheap Co3O4 catalyst, and provides an effective and economic solution to obtain excellent electrocatalysts for metal-air batteries.