Strain-Engineering of Mesoporous Cs 3 Bi 2 Br 9 /BiVO 4 S-Scheme Heterojunction for Efficient CO 2 Photoreduction.

Slow charge kinetics and unfavorable CO 2 adsorption/activation strongly inhibit CO 2 photoreduction. In this study, a strain-engineered Cs 3 Bi 2 Br 9 /hierarchically porous BiVO 4 (s-CBB/HP-BVO) heterojunction with improved charge separation and tailored CO 2 adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs 3 Bi 2 Br 9 can significantly downshift the p-band center of the active Bi atoms, which enhances the adsorption/activation of inert CO 2 . 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 CO 2 photoreduction undergoes a formaldehyde-mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite.