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 24O 31Br 11at around 750°C and the formed Bi 24O 31Br 11 can further convert to rod-like a-Bi 2O 3 at around 850°C. The prepared compounds were characterized with X-ray diffraction (XRD), N 2physical 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 (?>420 nm) and UV light (?=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 24O 31Br, Bi 24O 31Br, and a-Bi 2O 3, respectively. Under both UV light and visible light irradiation, the photocatalytic activity follows the order: BiOBr/Bi 24O 31Br mixture>BiOBr>Bi 24O 31Br>a-Bi 2O 3. The change in photocatalytic activity could be attributed to the different light absorption ability and microstructures of the photocatalysts. © 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.