Fabrication of WO3 nanorod arrays modified by BiOBr and their enhanced photoelectrocatalytic activity

BiOBr/WO3 nanorod array (NRA) composite photoelectrodes were successfully prepared using a solvothermal method. The instrumental characterisation of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, incident photoelectric conversion efficiency and ultraviolet diffuse reflectance indicates that the obtained BiOBr/WO3 NRAs exhibit good crystallinity and purity, and they can utilise light with wavelengths less than approximately 440 nm. On the surface of the WO3 nanorods, BiOBr thin nanosheets grow uniformly with strong adhesion and a 3D structure. The composite photoelectrode loaded with an appropriate amount of BiOBr (labelled BW-1 NRA) exhibits the best photoelectrocatalytic (PEC) activity. The PEC degradation efficiency of 10 mg/L of bisphenol A reached 95.7 % after 3 h at 1.0 V bias voltage. This value is 2.8 times that of individual photocatalytic degradation. After four times of recycling, the decrease in catalytic activity is insignificant, indicating the good stability of the catalyst. By analysing the results of the photoelectrochemical properties, band structures and types of free radicals, a conclusion is drawn that the excellent catalytic performance of BW-1 NRA is ascribed to the following aspects. (1) The formation of the p-n heterojunction by BiOBr and WO3 can effectively separate photogenerated electrons and holes. (2) Bias drives the migration of photogenerated electrons to the external circuit, further preventing the recombination of photogenerated electrons and holes. (3) The 3D structure of the photoelectrode has a large specific surface area and multiple active sites, improving light absorption and utilisation efficiency.