Co3O4/Mn3O4 hybrid catalysts with heterointerfaces as bifunctional catalysts for Zn-air batteries

Abstract

Zinc-air batteries (ZABs) with high energy density and safety are promising as next-generation energy storage systems, while their applications are severely hindered by the sluggish reaction kinetic of air cathodes. Developing a bifunctional catalyst with high activity and durability is an effective strategy to address the above challenges. Herein, a Co3O4/Mn3O4 nanohybrid with heterointerfaces is designed as advanced cathode catalyst for ZABs. Density functional theory calculations show the heterogeneous interface between Co3O4/Mn3O4 can improve the dynamics of carrier transport and thus enhancing the catalytic activity and durability. The Co3O4/Mn3O4 catalyst anchored on reduced graphene oxide (rGO) exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential of 0.86 V, and excellent oxygen evolution reaction (OER) activity with the potential of 1.59 V at 10 mA cm−2, which are comparable to the commercial noble metal catalysts. The improved ORR/OER catalytic activity is ascribed to the synergistic effect of heterointerfaces between Co3O4 and Mn3O4 as well as the improved conductivity and contact area of oxygen/catalysts/electrolytes three-phase interface by rGO. Furthermore, a home-made ZAB based on Co3O4/Mn3O4/rGO shows a high open circuit voltage of 1.54 V, a large power density of 194.6 mW cm−2 and good long-term cycling stability of nearly 400 h at 5 mA cm−2, which affords a promising bifunctional oxygen catalyst for rechargeable ZABs.