Amplified internal electric field of Cs2CuBr4@WO3−x S-scheme heterojunction for efficient CO2 photoreduction

Heterojunction construction, especially S-scheme heterojunction, represents an efficient universal strategy to achieve high-performance photocatalytic materials. For further performance stimulation of these well-designed heterojunctions, modulating the interfacial internal electric field (IEF) to steer dynamic charge transfer represents a promising approach. Herein, we realized the precise regulation of Fermi level ( E F ) of the oxidation semiconductor (mesoporous WO 3− x ) by tailoring the concentration of oxygen vacancies (V O ), maximizing the IEF intensity in Cs 2 CuBr 4 @WO 3− x (CCB@WO 3− x ) S-scheme heterojunction. The augmented IEF affords a robust driving force for directional electron delivery, leading to boosted charge separation. Hence, the developed CCB@WO 3− x S-scheme heterojunction demonstrated outstanding photocatalytic CO 2 reduction performance, with the electron consumption rate ( R electron ) up to 390.34 μmol g −1 h −1 , which is 3.28 folds higher than that of pure CCB. An in-depth analysis of the S-scheme electron transfer mode was presented via theoretical investigations, electron spin resonance (ESR), photo-irradiated Kelvin probe force microscopy (KPFM), and in-situ X-ray photoelectron spectroscopy (XPS). Finally, the CO 2 photoconversion route was explored in detail using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and DFT theoretical calculations.