Citric acid-assisted synthesis of nano-Ag/BiOBr with enhanced photocatalytic activity

In this study, silver nano-particles have been anchored in the surface of BiOBr photocatalysts by a citric acid-assisted photoreduction method. The citric acid was served as a chelating and reductive agent for the preparation of Ag-decorated BiOBr photocatalysts (named as Ag/BiOBr-2). The as-synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis diffuse reflection spectroscopy (DRS). The Ag/BiOBr-2 photocatalyst exhibited excellent and stable photocatalytic activities on MO and phenol degradation under simulated sunlight irradiation. The enhanced photocatalytic activity could be ascribed to the smaller size, rough surface, and the surface plasma resonance (SPR) effect of Ag. Also, the Schottky junction, between the surface of the BiOBr and silver nanoparticles, accelerated the efficient transfer and separation of photoinduced electron-hole pairs and promoted the photocatalytic performance. The active species tests indicated that the superoxide radical (center dot O-2 (-)) was responsible for the enhanced photocatalytic performance of Ag/BiOBr-2. Finally, a possible photocatalytic mechanism was proposed.