Room-temperature fabrication of bismuth oxybromide/oxyiodide photocatalyst and efficient degradation of phenolic pollutants under visible light

Bismuth oxybromide/oxyiodide (Bi4O5BrxI2-x) photocatalysts were successfully fabricated using a facile homogeneous precipitation method at room temperature. The obtained Bi4O5BrxI2-x demonstrated highly enhanced visible-light performances compared with Bi4O5Br2 and Bi4O5I2. The poducts were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and transmission electron microscope (TEM). The DRS analysis shows that the band gap structures of Bi4O5BrxI2-x have been gradually modulated by changing the Br/I molar ratio. The obtained Bi4O5BrxI2-x samples have exhibited efficient photocatalytic activities in decomposing resorcinol, o-phenylphenol, and 4-tert-butylphenol. The Br/I molar ratio has great influence on the activity of the photocatalysts, and Bi4O5Br0.6I1.4 exhibited the best activity which was about 2.77 and 1.80 times higher than that of Bi4O5Br2 and Bi4O5I2, respectively. The degradation intermediates were identified by liquid chromatography-mass spectrometry (LCMS), and the possible degradation pathway of resorcinol over Bi4O5BrxI2-x photocatalysts was proposed. The strong visible light absorption, high charge separation efficiency, and proper band potentials should be responsible for the excellent activity of Bi4O5BrxI2-x photocatalyst. Trapping experiments using radical scavengers confirmed the generation of O2-, OH, and h+, but only O2- and h+ have played the chief role in removing organic pollutants from water.