Realizing Unassisted Photo-Charging of Zinc-Air Batteries by Anisotropic Charge Separation in Photoelectrodes.

Kong, Lingqiao; Ruan, Qiushi; Qiao, Jingyuan; Chen, Pengyu; Yan, Bingzhen; He, Wei; Zhang, Wei; Jiang, Chaoran et al. · Adv Mater · 2023

basic_science · Level V

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Abstract

Solar rechargeable zinc-air battery is a promising approach for capturing and storing intermittent solar energy through photoelectrochemical reactions. However, unassisted photo-charging of zinc-air batteries is challenging due to suboptimal carrier accumulation on photoelectrodes, resulting in sluggish reaction kinetics. Here, unassisted photo-charging of zinc-air battery is achieved by investigating anisotropic photogenerated charge separation on a series of representative semiconductors (ZnIn<sub>2</sub> S<sub>4</sub> , TiO<sub>2</sub> , and In<sub>2</sub> O<sub>3</sub> ), among which the exceptional anisotropic charge separation on a ZnIn<sub>2</sub> S<sub>4</sub> photoelectrode is revealed based on anisotropic charge diffusion capabilities. The charge separation is facet-dependent, which is observed using Kelvin probe force microscopy, verifying a cause-and-effect relationship between the photo-charge accumulation on photoelectrodes and their photo-charging performance in zinc-air batteries. This work achieves an unassisted photo-charging current density of 1.9 mA cm<sup>-2</sup> with a light-to-chemical energy conversion efficiency of 1.45%, highlighting the importance of anisotropic semiconductors for unassisted photo-charging of zinc-air batteries via efficient photogenerated charge separation.