Engineering the Band Structure of Ag-Modified Bi2– x WO6 with Bi Vacancies Enhances the Photocatalytic Activity and High Selectivity of CO2 Reduction to CH4

Abstract The development of efficient photocatalysts to convert carbon dioxide into renewable fuels is crucial for mitigating the greenhouse effect and addressing the energy crisis. However, the slow migration rate of photogenerated charge carriers remains one of the main factors limiting the efficiency of this process. In this study, we successfully fabricated a Mott–Schottky-type Ag/Bi2–xWO6 heterostructured photocatalyst by in situ growth of Ag nanoparticles on Bi2WO6 substrates containing bismuth vacancies (Bi2–xWO6), thereby increasing the photocatalytic reduction efficiency of CO2. The flower-like morphology of Bi2–xWO6 provides abundant active sites, while the Bi vacancies facilitate CO2 adsorption on the material. Furthermore, after loading with Ag nanoparticles, an Ag/Bi2WO6 Mott–Schottky junction forms at the interface, enabling electrons from the conduction band of Bi2–xWO6 to transfer to the Ag nanoparticles, thus lowering the recombination rate of photogenerated electrons and holes. Overall, the Ag/Bi2–xWO6 heterostructure exhibits excellent photocatalytic activity for CO2 reduction. Notably, compared with those of pure Bi2WO6, the CO/CH4 generation rates of 30Ag/Bi2–xWO6 reached 17.7/13.7 μmol g–1·h–1, and the total electron consumption rate (Relectron) exhibited a 17.54-fold increase. This work provides a paradigm for designing Ag-modified and bismuth vacancy-based photocatalysts for solar-driven CO2 reduction.