Ag₂S quantum-dot-modified flower-like PbBiO₂Br for enhanced photocatalytic degradation of crystal violet

Novel Ag₂S/PbBiO₂Br (Ag₂S/PBOB) direct Z-scheme photocatalysts were successfully synthesized for the first time by modifying flower-like PBOB with Ag₂S QDs through a hydrothermal and ion-exchange way. The crystal structure, surface state, morphology, element distribution, electrochemical and optical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), photocurrent testing, Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL) technique. The obtained samples were evaluated via degradation of crystal violet (CV) under visible light irradiation. The results show that direct Z-scheme heterojunctions are formed on the interfaces between Ag₂S and the PBOB, which enhance the visible light absorbance and efficient separation of photo-generated electron–hole pairs. Moreover, the 5wt%Ag₂S/PBOB composite displays the highest photocatalytic activity for the degradation of CV under visible light, where the CV degradation rate is 94.4%, about 1.37 times higher than that for bare PBOB under visible light irradiation for 60 min. The enhanced photocatalytic activity of the Ag₂S/PBOB composites can be attributed to strong visible light absorbance and the direct Z-scheme charge transfer mechanism. Moreover, the 5wt%Ag₂S/PBOB composite also has a good stability and recyclability and has great potential in environmental protection. In addition, active species trapping experiments confirm that ·O₂ and ·OH play a very important role in the degradation process. This work provides new insights and opportunities for establishing photocatalytic models in degradation of organic contaminant.