Direct utilization of light energy to promote the power density of zinc–air batteries using Co3O4@CuxO air photocathodes with porous octahedral superstructures

Abstract

The commercialization of zinc–air batteries (ZABs) is essentially limited by low power density as well as poor cycling stability. Herein, photo-sensitive air cathode materials composed of Cu_xO (referred to as CuO/Cu₂O) and Co₃O₄ with porous octahedral superstructures were prepared to promote the power density of ZABs. The highly electroactive Co₃O₄ species were grown against the Cu_xO octahedral particles through heat treatment, forming a homogeneous interspersion of Co₃O₄ and Cu_xO (Co₃O₄@ Cu_xO) with a reduced Gibbs free energy for OOH*. In virtue of the enhanced light absorption, enriched electroactivity, porous superstructures, and lower energy barrier, the as-prepared Co₃O₄@Cu_xO air photocathode can achieve a lower charge potential of 1.759 V than that obtained without light (1.886 V), exhibiting a considerable energy saving of 6.7%. Moreover, the fabricated ZAB cells can deliver a maximum specific capacity of 759.12 mA h g⁻¹ with a high power density of 76 mW cm⁻², corresponding to light enhancements of 7.24% and 31%, respectively. The as-fabricated ZABs also exhibited a good stability up to 160 hours under light irradiation, indicating a promising direct utilization of light energy for ZAB cells.