Synthesis, mechanism and characterization of SiO2/BiOX (X = Br, Cl): efficient photocatalytic degradation of various antibiotics under visible-light irradiation

BiOXs (X = Br, Cl, I, F) are extensively used visible-light-driven photocatalysts and used widely, but except for BiOF, they exhibit an indirect bandgap, and electrons need to cross the K layer to enter the conduction band, which greatly reduces electron-hole complexation. To enhance the photocatalytic activity of BiOXs, we prepared a series of BiOXs materials modified with mesoporous SiO2 using a hybrid solvothermal method with microwave assistance. It was demonstrated using XRD, SEM, XPS, UV-vis DRS, and PL methods that the two-dimensional layered BiOXs were successfully complexed with mesoporous SiO2 forming highly active photocatalysts. Under simulated visible-light conditions, the SiO2/BiOXs materials showed very high degradation efficiency for ofloxacin (OFL) and tetracycline hydrochloride (TCH). The photocatalytic degradation efficiency of both SiO2/BiOCl and SiO2/BiOBr for OFL and TCH was up to 100%. The enhanced activity of the photocatalyst was attributed to the formation of a heterogeneous interface between mesoporous SiO2 and two-dimensional layered bismuth halide oxides, thus improving the separation rate of photogenerated carriers. The introduction of mesoporous SiO2 provided more adsorption sites and active sites for antibiotic molecules improving the adsorption performance of BiOX. In addition, the quenching experiments showed that center dot O-2(-) was the main reactant for OFL and TCH. This study demonstrates feasible preparation of low-cost, simple, and efficient photocatalysts, offering promising application potential for photocatalytic degradation of antibiotic contaminants in water.