Three-dimensionally ordered Co3O4@WO3 composite arrays as a binder-free air cathode for high-performance Zn-air batteries

Abstract

The development of low-cost, stable, and highly-active bifunctional catalysts is an important step to realize high-performance rechargeable Zn-air batteries. Herein, we report an innovative air cathode of three-dimensionally (3D) ordered macroporous Co3O4@WO3 composite arrays on a flexible carbon cloth substrate prepared by the decoration of Co3O4 nanosheets on electrodeposited macroporous WO3 inverse opals. Benefiting from a high specific surface area, rich active sites, and a facilitated charge/mass transfer process provided by the 3D ordered macroporous structure, the as-prepared Co3O4@WO3 composite exhibits excellent bifunctional catalytic activity with a half-wave potential of 0.75 V for oxygen reduction reaction and an overpotential of 339 mV at 10 mA/cm2 for oxygen evolution reaction, contributing to a low oxygen potential gap (ΔE) of 0.81 V. Furthermore, Co3O4@WO3 composite arrays are directly used as a binder-free air cathode for rechargeable Zn-air batteries, ensuring excellent mechanical and electrochemical stability. The aqueous Zn-air batteries based on 3D Co3O4@WO3 air cathodes exhibit excellent performance, in terms of a high specific capacity of 828.6 mAh/gZn1 at 5 mA/cm2 and long-term cycling stability of over 646 h.