Utilizing solar energy to improve the oxygen evolution reaction kinetics in zinc-air battery.

Directly harvesting solar energy for battery charging represents an ultimate solution toward low-cost, green, efficient and sustainable electrochemical energy storage. Here, we design a sunlight promotion strategy into rechargeable zinc-air battery with significantly reduced charging potential below the theoretical cell voltage of zinc-air batteries. The sunlight-promoted zinc-air battery using BiVO4 or α-Fe2O3 air photoelectrode achieves a record-low charge potential of ~1.20 and ~1.43 V, respectively, under illumination, which is lowered by ~0.5-0.8 V compared to the typical charge voltage of ~2 V in conventional zinc-air battery. The band structure and photoelectrochemical stability of photoelectrodes are found to be key factors determining the charging performance of sunlight-promoted zinc-air batteries. The introduction of photoelectrode as an air electrode opens a facile way for developing integrated single-unit zinc-air batteries that can efficiently use solar energy to overcome the high charging overpotential of conventional zinc-air batteries.