Inbuilt photoelectric field of heterostructured cobalt/iron oxides promotes oxygen electrocatalysis for high-energy-efficiency zinc-air batteries

The practical application of zinc-air batteries (ZABs) is limited by the large overpotentials generated by the sluggish kinetics of oxygen electrocatalysis at air electrodes. To address this challenge, we report a photocathode composed of Fe2O3/Co3O4 mixed metal oxides for photo-assisted rechargeable ZABs. Owing to the formation of Fe2O3/Co3O4 heterostructures with abundant oxygen vacancies (Vox), the air electrode exhibited a high surface photovoltage (SPV) of 220 mV based on the contact potential difference (CPD) recorded before and after light irradiation, corresponding to a very high specific SPV of 44 kV m-1. Consequently, the photo-rechargeable ZABs incorporating this Fe2O3/Co3O4 air photocathode exhibit a low charge potential of 1.6 V under light irradiation. Furthermore, these ZABs demonstrate a remarkable increase in energy efficiency, from 64% to 78%, coupled with a high specific capacity of 712.3 mAh g-1 and excellent stability over a span of 60 hours. This achievement underscores the potential for harnessing light energy in the next generation of ZABs, suggesting the promise of a brighter future for energy storage technologies.