Reversed Electron Transfer in Cu‐TiO ₂ @ZnIn ₂ S ₄ for Boosting Photocatalytic CO ₂ Reduction

Abstract Spontaneous free‐electron transfer significantly affects the photocatalytic performance of carbon dioxide (CO 2 ) reduction. However, the precise regulation of photogenerated electron transfer direction remains a nontrivial endeavor. Herein, a heteroatomic metal‐dependent strategy is proposed to direct photogenerated electron transfer to specific catalytic active sites, thus enhancing CO 2 photoreduction over Cu‐TiO 2 @ZnIn 2 S 4 (Cu‐TiO 2 @ZIS). The core‐shell Cu‐TiO 2 @ZIS heterojunction with high activity is fabricated by in situ growth. Impressively, the optimized Cu‐TiO 2 @ZIS photocatalyst exhibits a remarkable visible light driven CO 2 ‐to‐carbon monoxide (CO) production rate of 620 µmol g −1 h −1 with selectivity (99.4%), representing a 77.5‐fold and 6.3‐fold enhancement over pristine TiO 2 (8 µmol g −1 h −1 ) and ZIS (99 µmol g −1 h −1 ), respectively. In situ characterization and theoretical calculations reveal that the combination of Cu‐TiO 2 and ZnIn 2 S 4 forms a strong interface electric field and regulates the direction of electron transfer due to the work function difference. Cu sites induce the transfer of photogenerated electrons from ZIS to Cu‐TiO 2 to generate electron‐rich Cu/Ti active sites, increasing the adsorption energy of CO 2 on Cu/Ti sites. Moreover, Cu‐TiO 2 @ZIS significantly reduces Gibbs free energy barriers for *COOH intermediate formation, thereby enhancing the photocatalytic performance of CO 2 reduction. This work exemplifies a new strategy for designing high‐active photocatalysts by manipulating heteroatomic metal‐dependent electron transfer.