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 2 -In 2 Se 3 ) 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 2 -In 2 Se 3 heterojunction is exposed to light, photogenerated electrons at the conduction band (CB) of TiO 2 migrate to the valence band (VB) of In 2 Se 3 due to the built-in electric field. The photogenerated electrons with strong reduction capability on the CB of In 2 Se 3 and the holes with strong oxidation capability on the VB of TiO 2 boost the cathode reaction kinetics (ORR/OER). The excellent outcome reveals tremendous commercial potential of photo-enhanced Zn-air batteries.