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 CO2. However, the fast carrier recombination rates and inadequate adsorption/activation for CO2 molecules have seriously restricted their practical application. Herein, an innovative step-scheme-based Cs2CuBr4/TiO2 (CCB/TiO2) photocatalyst was prepared by embedding Cs2CuBr4 PQDs in a mesoporous TiO2 matrix, which exhibits considerable potential as candidates for CO2 photoreduction under simulated sunlight. Remarkably, the optimised CCB/TiO2 photocatalyst delivered an impressive CO2 reduction activity, which was 3.1 and 16.0 times higher than those achieved by pure Cs2CuBr4 and TiO2, 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/TiO2 exhibited a reduced energy barrier of the rate-determining step, which facilitated the CO2 photoreduction reaction.