Strain‐Engineering of Mesoporous Cs3Bi2Br9/BiVO4 S‐Scheme Heterojunction for Efficient CO2 Photoreduction

Slow charge kinetics and unfavorable CO2 adsorption/activation strongly inhibit CO2 photoreduction. In this study, a strain‐engineered Cs3Bi2Br9/hierarchically porous BiVO4 (s‐CBB/HP‐BVO) heterojunction with improved charge separation and tailored CO2 adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs3Bi2Br9 can significantly downshift the p‐band center of the active Bi atoms, which enhances the adsorption/activation of inert CO2. Meanwhile, in situ irradiation X‐ray photoelectron spectroscopy and electron spin resonance confirm that efficient charge transfer occurs in s‐CBB/HP‐BVO following an S‐scheme with built‐in electric field acceleration. Therefore, the well‐designed s‐CBB/HP‐BVO heterojunction exhibits a boosted photocatalytic activity, with a total electron consumption rate of 70.63 µmol g−1 h−1, and 79.66% selectivity of CO production. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy reveals that CO2 photoreduction undergoes a formaldehyde‐mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite. The strain‐engineered Cs3Bi2Br9/hierarchically porous BiVO4 S‐scheme heterojunction is fabricated through a one‐step selective etching coupling with in situ transformation of Bi2O3 strategy, using well‐integrated Bi2O3‐BiVO4 composite nanosphere as support and Bi source, which results in improved charge separation and tailored CO2 adsorption/activation capability and achieves efficient photocatalytic CO2 reduction.