In‐Situ Generated CsPbBr3 Nanocrystals on O‐Defective WO3 for Photocatalytic CO2 Reduction

Abstract Metal halide perovskite (MHP) nanocrystals (NCs) have shown promising application in photocatalytic CO 2 reduction, but their activities are still largely restrained by severe charge recombination and narrow solar spectrum response. Assembly of heterojunctions can be beneficial to the charge separation in MHPs while the assembly process usually brings native interfacial defects, impeding efficient charge separation between two materials. Herein, an in‐situ generation strategy was developed to prepare CsPbBr 3 /WO 3 heterojunction, using WO 3 nanosheets (NSs) as growing substrate for the growth of CsPbBr 3 NCs. The developed CsPbBr 3 /WO 3 heterojunction exhibited a high‐quality interface, greatly facilitating charge transfer between two semiconductors. The hybrid photocatalyst displayed an excellent activity toward CO 2 reduction, which was about 7‐fold higher than pristine CsPbBr 3 NCs and 3.5‐fold higher than their assembled counterparts. The experimental results and theoretical simulations revealed that a Z‐scheme mechanism with a favorable internal electric field was responsible for the good performance of CsPbBr 3 /WO 3 heterojunction. By using O‐defective WO 3 NSs as a near‐infrared (NIR) light absorber, the CsPbBr 3 /WO 3 heterojunction could harvest NIR light and showed an impressive activity toward CO 2 reduction. This work demonstrates a new strategy to design MHP‐based heterojunctions by synergistically considering the interface quality, charge transfer mode, interfacial electric field, and light response range between two semiconductors.