A very low charge potential for zinc-air battery promoted by photochemical effect of triazine-based conjugated polymer nanolayer coated TiO2

Photochemical-assisted rechargeable batteries are suffering from a high charge potential due to unfavorable surface charge kinetics of photochemical electrodes, that is surface defects induced energy loss. In this work, in-situ growing thickness-controlled polymer nanolayer on TiO2 nanorods electrode by a facile solvothermal reaction optimizes surface states conditions via mitigating oxygen vacancy induced hole trapping agents, while polymer nanolayer creates abundant active surface states that efficiently extract holes for photooxidation reaction. For modified photoelectrodes, 8 times improvement in interfacial charge transfer/recombination ratio (Kt/Kr) at a low applied bias contributes to a low onset potential (0.2 V vs. RHE) for photooxidation and shows 12 times improvement in photocurrent density at 0.4 V vs. RHE under simulated sunlight irradiation (AM 1.5 G, 100 mW cm−2) than that of r-TiO2, which contributes to the superior performance of a photochemical-assisted rechargeable Zn-air battery (PZAB). Equipping such a photoelectrode can photo-charge the battery at 10 mA cm−2 with a record-low potential of 0.8 V, saving 76.5% electrical energy. The electrode shows excellent stability for a 10-h cycling test. This work provides scientific thoughts and synthetic strategies for a highly efficient solar-rechargeable electric energy storage system and expands the scope of application for conjugated polymers.