Novel two-step synthesis method of thin film heterojunction of BiOBr/Bi2WO6 with improved visible-light-driven photocatalytic activity

A novel two-step ionic liquid assisted procedure was applied for a controllable synthesis of BiOBr/Bi2WO6 heterojunction thin films. The preparation route involved an anodic oxidation of tungsten foil and hydrothermal transformation of as-anodized oxide in the presence of bismuth precursor and ionic liquid, N-butylpyridinium bromide [BPy][Br]. The BiOBr plates with irregular shapes adhered to the surface of flower-like Bi2WO6 and formed a heterojunction between BiOBr and Bi2WO6, as confirmed by the analysis of their structure and composition. The highest efficiency of phenol degradation was achieved when the highest amount of IL was used (the apparent quantum efficiency was almost 8 and 71.5 times higher compared to BiOBr and Bi2WO6, respectively). In addition, superoxide radicals (O-center dot(2)-) were found as the main factor responsible for the photo-degradation. A possible reaction mechanism was further investigated as a function of monochromatic irradiation to determine the exact range of the composite photoactivity.

Automated summary

In this study, a novel two-step ionic liquid assisted procedure was used for the controllable synthesis of BiOBr/Bi2WO6 heterojunction thin films. The presence of ionic liquid significantly affected the efficiency of phenol degradation, with superoxide radicals identified as the main factor responsible for the photo-degradation. The study also investigated a possible reaction mechanism and the exact range of composite photoactivity under monochromatic irradiation.