A Highly Reversible Sn-Air Battery Possessing the Ultra-Low Charging Potential with the Assistance of Light.

Aqueous Sn-air batteries are attracting a great deal of interest in recent years due to the ultra-high safety, low cost, dendrite-free and highly reversible Sn anode. However, the slurry oxygen reduction/evolution reaction (ORR/OER) kinetics on the air cathodes seriously affect the Sn-air battery performances. Although various advanced catalysts have been developed, the charge overpotentials (~1000 mV) of these Sn-air batteries are still not satisfactory. Herein, iron oxide (Fe 2 O 3 ) modified titanium dioxide (TiO 2 ) nanorods with heterogeneous structure are firstly synthesized on Ti mesh (Fe 2 O 3 @TiO 2 /Ti), and the obtained Fe 2 O 3 @TiO 2 /Ti films are further applied as catalytic electrodes for Sn-air batteries. The core-shell heterogeneous structure of Fe 2 O 3 @TiO 2 /Ti can effectively facilitate the conversion of electrochemical intermediates and separation of photo-excited electrons and holes to activate oxygen-related reaction processes. Density functional theory (DFT) and experimental results also confirm that Fe 2 O 3 @TiO 2 /Ti can not only act as the electrocatalysts to improve ORR/OER properties, but also exhibit the superior photo-catalytic activity to promote charging kinetics. Hence, the Fe 2 O 3 @TiO 2 /Ti-based Sn-air batteries show ultra-low overpotential of ~40 mV, excellent rate capability and good cycling stability under light irradiation. This work will shed light on rational photo-assisted catalytic cathode design for new-type metal-air batteries.