Decreasing the charging voltage of a zinc-air battery using a bifunctional W:BiVO4/V2O5 photoelectrode and sulfite as a sacrificial agent

Abstract The promising potential of rechargeable Zn-air battery as energy storage technology is followed by relevant limitations, such as its high charging overpotential that restricts its feasibility. In such a way, replacing the battery electrocatalyst for a photoelectrode can offer a double advantage compared to conventional rechargeable metal-air batteries: (i) to act more efficiently in the oxidation reaction involved in the charging process, and (ii) to reduce the charging bias using sunlight. Herein, we report for the first time a BiVO4-based photoelectrode as the bifunctional electrode of a zinc-air battery. The novel photoelectrochemical battery consisting of a W:BiVO4/V2O5 photoelectrode in a sulfite solution and a Zn electrode in an alkaline medium can have its charging voltage reduced up to 1.2 V under visible-light illumination. In discharge mode, where the photoanode electrode plays the role of air electrode, the system can deliver power with an open-circuit potential of 1.1 V.