Mesoporous TiO2 matrix embeded with Cs2CuBr4 perovskite quantum dots as a step-scheme-based photocatalyst for boosting charge separation and CO2 photoconversion

Halide perovskite quantum dots (PQDs) have shown great promise for the photochemical conversion of CO 2 . However, the fast carrier recombination rates and inadequate adsorption/activation for CO 2 molecules have seriously restricted their practical application. Herein, an innovative step-scheme-based Cs 2 CuBr 4 /TiO 2 (CCB/TiO 2 ) photocatalyst was prepared by embedding Cs 2 CuBr 4 PQDs in a mesoporous TiO 2 matrix, which exhibits considerable potential as candidates for CO 2 photoreduction under simulated sunlight. Remarkably, the optimised CCB/TiO 2 photocatalyst delivered an impressive CO 2 reduction activity, which was 3.1 and 16.0 times higher than those achieved by pure Cs 2 CuBr 4 and TiO 2 , respectively. Furthermore, the S-scheme charge transfer mode was comprehensively corroborated by density functional theory (DFT) calculations, photo-assisted Kelvin probe force microscopy (KPFM), in situ irradiated X-ray photoelectron spectra (XPS), and electron spin resonance spectroscopy (ESR). On basis of theoretical calculations and in situ diffuse reflectance spectra (DRIFTS), the CCB/TiO 2 exhibited a reduced energy barrier of the rate-determining step, which facilitated the CO 2 photoreduction reaction.