Synergistic Effect of S-Scheme Charge Transfer and Photothermal Conversion in Cs3Bi2Br9/Bi2Se3 Heterojunction for Boosted CO2 Photoreduction

Abstract The escalating anthropogenic CO2 emissions have triggered severe environmental crises, making the development of efficient photocatalytic CO2 reduction technologies crucial for carbon neutrality. Herein, an S-scheme heterojunction photocatalyst was successfully constructed by anchoring Cs3Bi2Br9 perovskite quantum dots (CBB PQDs) onto Bi2Se3 nanosheets via electrostatic assembly. The S-scheme charge transfer mechanism, verified by Mott–Schottky analysis, ultraviolet photoelectron spectroscopy (UPS), in situ X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations, efficiently suppressed electron-hole recombination while retaining robust redox potentials of photogenerated carriers. Additionally, Bi2Se3 enabled the heterojunction to reach a surface temperature of 131.2 °C within 6 min under ultraviolet-visible-near-infrared (UV-Vis-NIR) irradiation, concomitantly lowering the activation energy barrier for CO2 reduction. The synergistic effect of S-scheme charge transfer and photothermal conversion in the CBB/Bi2Se3 heterojunction led to boosted CO2 photoreduction: photocatalytic tests showed that the optimized 50% CBB/Bi2Se3 heterojunction achieved a CO yield rate of 134.93 μmol g–1 h–1. Furthermore, the reaction pathway was revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This work provides a rational design strategy for perovskite-based photothermal catalysts, highlighting their potential in solar-driven CO2 conversion to value-added chemicals.