Thermal Stability, Microstructure and Photocatalytic Activity of the Bismuth Oxybromide Photocatalyst

Abstract Flake BiOBr was first prepared by a solution method at room temperature. Then, the produced BiOBr was calcined at different temperatures. It was found that BiOBr is not a stable compound. It transforms to plate‐like Bi 24 O 31 Br 11 at around 750°C and the formed Bi 24 O 31 Br 11 can further convert to rod‐like α ‐Bi 2 O 3 at around 850°C. The prepared compounds were characterized with X‐ray diffraction (XRD), N 2 physical adsorption, scanning electron microscopy (SEM), and UV‐Vis diffuse reflectance spectra (DRS), respectively. The photocatalytic activity of the produced bismuth oxybromides was evaluated by photocatalytic decomposition of acid orange II under both visible light ( λ >420 nm) and UV light ( λ =365 nm) irradiation. Results show that these compounds have different band gaps and different photocatalytic properties. The band gap energies of the as‐prepared samples were found to be 2.82, 2.79, 2.60 and 3.15 eV for BiOBr, BiOBr/Bi 24 O 31 Br, Bi 24 O 31 Br, and α ‐Bi 2 O 3 , respectively. Under both UV light and visible light irradiation, the photocatalytic activity follows the order: BiOBr/Bi 24 O 31 Br mixture>BiOBr>Bi 24 O 31 Br> α ‐Bi 2 O 3 . The change in photocatalytic activity could be attributed to the different light absorption ability and microstructures of the photocatalysts.