Surfactant-assisted synthesis of direct Z-scheme AgBr/β-Ag₂WO₄ heterostructures with enhanced visible-light-driven photocatalytic activities

Compared with the conventional two-step ion exchange method used for the fabrication of AgBr/β-Ag₂WO₄ heterostructures, herein, a series of AgBr/β-Ag₂WO₄ direct Z-scheme heterostructures were efficiently fabricated via a simple surfactant-assisted one-step precipitation strategy. The phase structure, morphology, chemical composition as well as photocatalytic mechanism of the as-obtained AgBr/β-Ag₂WO₄ heterostructures were systematically characterized by using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Ultraviolet–Visible diffuse reflectance spectra (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectrum (PL), photoelectrochemical tests. Photocatalytic degradation of Rhodamine (RhB) under visible light was carried out as a probe to assess its photocatalytic activity. The result indicates that AgBr/β-Ag₂WO₄-30% exhibits the highest photocatalytic activity, which is approximately 1.7 and 135.9 times as high as that of pure AgBr and pure β-Ag₂WO₄, respectively. The pathway of charge carriers separation and transfer in the AgBr/β-Ag₂WO₄ heterostructures and the direct Z-scheme mechanism were depicted in details based on the systematic characterizations and measurements. The enhancement of the photocatalytic performances of the as-prepared AgBr/β-Ag₂WO₄ heterostructures are mainly attributed to the larger specific surface area and Z-scheme system formed between these two semiconductors, leading to the spatial separation of the photoinduced electron and hole. This work may provide a new sight to understand the mechanism of AgBr/β-Ag₂WO₄ heterostructures, which is direct Z-scheme heterojunctions rather than type-II heterojunctions.