Photo Energy-Enhanced Oxygen Reduction and Evolution Kinetics in Zn-Air Batteries.

Harvesting solar energy directly to boost the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on an air cathode is a promising approach. Herein, we synthesize a step-scheme (S-scheme) titanium dioxide-indium selenide (TiO-InSe) heterojunction catalyst. The onset potential in ORR under light illumination reaches 1.28 V and the onset potential decreases to 0.48 V in OER. When an S-scheme TiO-InSe heterojunction is exposed to light, photogenerated electrons at the conduction band (CB) of TiO migrate to the valence band (VB) of InSe due to the built-in electric field. The photogenerated electrons with strong reduction capability on the CB of InSe and the holes with strong oxidation capability on the VB of TiO boost the cathode reaction kinetics (ORR/OER). The excellent outcome reveals tremendous commercial potential of photo-enhanced Zn-air batteries.