Effect of reaction mediums on photocatalytic performance of BiOX (X = Cl, Br, I)

Although BiOX (X = Cl, Br, I) have been reported to be synthesized in various solvents and exhibited solventdependent photocatalytic performance, systematical investigation on how the solvents affected energy band structure and microstructure of BiOX keeps challenging. Herein, BiOX photocatalysts were prepared in various solvents, including deionized water, glacial acetic acid, ethylene glycol, glycerol, urea solution, N, N-dimethylformamide, methanol and ethanol, at room temperature while keeping other reaction conditions identical. Their microstructure and band structure were characterized by XRD, SEM, DRS, Mott-Schottky curves, etc. And photocatalytic performance was assessed by using tetracycline (TC), rhodamine B (RhB) and methyl orange (MO) as simulated pollutants under both visible and ultraviolet (UV) light illumination. The results indicated that the effect of solvent-induced microstructures, such as morphology, particle size (specific surface areas) and facet exposure ratio, on photocatalytic performance of three BiOX is in the same change order. Whereas, the change of their band potentials is relatively inconsistent. Among the studied solvents, BiOX prepared in ethylene glycol (EG) showed the best photocatalytic activity, and those prepared in aqueous solution demonstrated the worst photocatalytic performance. In addition, for BiOX prepared in the same solvent, BiOCl and BiOBr exhibited higher photocatalytic activity for TC and RhB degradation than BiOI, whereas, they showed reversed trend for MO degradation.