3D Hierarchical ZnIn 2 S 4 Nanosheets with Rich Zn Vacancies Boosting Photocatalytic CO 2 Reduction

Zinc vacancy (V Zn ) is successfully introduced into 3D hierarchical ZnIn 2 S 4 (3D‐ZIS). The photo‐electrochemical experiments demonstrate that the charge separation and carrier transfer are more efficient in the 3D‐ZIS with rich V Zn . Of note, for the first time, it is found that V Zn can decrease the carrier transport activation energy (CTAE), from 1.14 eV for Bulk‐ZIS (Bulk ZnIn 2 S 4 ) to 0.93 eV for 3D‐ZIS, which may provide a feasible platform for further understanding the mechanism of photocatalytic CO 2 reduction. In situ Fourier transform infrared (FT‐IR) results reveal that the presence of rich V Zn ensures CO 2 chemical activation, promoting single‐electron reduction of CO 2 to CO 2 − . In addition, in situ FT‐IR and CO 2 temperature programmed desorption results show that V Zn can promote the formation of surface hydroxyl. To the best of current knowledge, there are no reports on the photoreduction of CO 2 simply by virtue of 3D‐ZIS with V Zn and few literature reports on the photocatalytic reduction of CO 2 concerned with CTAE. Additionally, this work finds that surface hydroxyl may play a crucial role in the process of CO 2 photoreduction. The work may provide some novel ways to ameliorate solar energy conversion performance and a better understanding of photoreaction mechanisms.