Unveiling the effect of interstitial dopants on CO2 activation over CsPbBr3 catalyst for efficient photothermal CO2 reduction

Halide perovskites, enabled by their superior light harvesting ability and high carrier mobility, have emerged as promising catalysts for solar CO2 reduction. However, the catalytic performance remains largely limited due to the challenge of efficient CO2 activation on pristine perovskite surface. Herein, we elaborately doped the CsPbBr3 with interstitial Cu ions to reveal the effect of dopants on the CO2 activation for photothermal CO2 reduction using H2O as the proton source. Initially, the interstitial Cu dopants would significantly suppress the charge carrier recombination in CsPbBr3, leaving more carriers to participate in the surface catalytic reactions. Meanwhile, the Cu dopants would modulate the surface sites for better adsorption and activation of CO2 molecules and CO intermediates, as evidenced by the results of CO2 and CO temperature-programed-desorption profiles. Furthermore, analysis of in-situ diffuse-reflectance infrared Fourier transform spectra (DRIFTS) and theoretical calculations indicates that the CO2 reduction to CH4 follows *COH pathway on Cu:CsPbBr3, but *CHO pathway on CsPbBr3, where the former is more thermodynamically favorable. It is then revealed that the Cu dopants would facilitate the CO2 reduction by supplying more carriers, adsorbing more CO2 molecules and catalyzing the CO2 dissociation more easily. As a result, our Cu:CsPbBr3 achieved an impressive activity of 14.72 μmol·g−1·h−1 for CH4 production and a CH4 selectivity of 96.9%, which are both higher than those of the pristine CsPbBr3 (3.62 μmol·g−1·h−1 and 81.1%). Our work provides an insightful understanding of the roles of dopants in the CO2 activation for photothermal catalytic CO2 reduction on halide perovskite catalysts.