Preparation of BiOBr-Bi heterojunction composites with enhanced photocatalytic properties on BiOBr surface by in-situ reduction

A new kind of BiOBr-Bi composite with improved photocatalytic capabilities was successfully prepared by in-situ reduction. The X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet–visible spectroscopy (UV–VisDRS), X-ray photoelectron spectroscopy (XPS), Brunner-Emmet-Teller measurements (BET), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and the electron paramagnetic resonance (EPR) were used to characterize the morphological structures, physical properties and surface element composition of the photocatalysts. In addition, photocatalytic activity was evaluated by degrading the antibiotic norfloxacin (NOR). The results showed that the BiOBr-Bi (40 mmol/L NaBH4) had the highest activity. The degradation rate reached 97.2%. The half-life of NOR was shortened to 25 min. Moreover, the results of capture experiments indicated that the main active groups involved in the photocatalytic process under visible light conditions were ·O2- and h+. The reason why the activity of the BiOBr-Bi material photocatalyst increased is that the heterojunction formed by BiOBr with wider bandgap and Bi metal with a lower Fermi level effectively inhibits the recombination of holes and photogenerated electrons, which leads to the enhancement of oxidation capacity.