Preparation of BiOBr thin films with micro-nano-structure and their photocatalytic applications

• The BiOBr film was prepared at low temperature via alcoholysis-coating method.
• The optimum process conditions of preparing BiOBr film were discussed.
• As-prepared BiOBr films were composed of micro-nano flake structures.
• The BiOBr films demonstrated excellent photocatalytic activity.
• The formation mechanism of BiOBr films with high activity was proposed.

A series of micro-nano-structure BiOBr thin films were prepared at a low temperature by the alcoholysis-coating method using BiBr3 as precursor. The as-prepared films were characterized by X-ray powder diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller surface area. The obtained results indicated that micro-nano-structure tetragonal BiOBr films with different intensity ratios of (110) to (102) characteristic peaks could be synthesized through controlling the reaction temperature and the calcination temperatures. Furthermore, the photocatalytic activities of BiOBr thin films with different preparation conditions have been evaluated by the degradation of methyl orange (MO) under UV light irradiation, suggesting that the photocatalytic activity should be closely related to the solvent, the alcoholysis reaction temperature, and the calcining temperature. The best photocatalytic degradation efficiency of MO for BiOBr thin films reaches 98.5% under 2.5 h UV irradiation. The BiOBr thin films display excellent stability and their photocatalytic activity still remains above 90% after being used five times. The main reasons for the higher photocatalytic activity of micro-nano-structure BiOBr microspheres have been investigated. In addition, the possible formation mechanism of BiOBr thin films with micro-nano-structure and excellent photocatalytic activity was proposed and discussed.