Hierarchical BiOBr, AgBr/BiOBr and BiOBrxI1-x Nano-Assembled Microspheres for Photocatalytic Methyl Orange Treatment

We prepared hierarchical BiOBr, AgBr/BiOBr and BiOBrxI1-x (x = 0.3, 0.5 and 0.7) microspheres in ethylene glycol by a solvothermal method, then analyzed them by scanning electron microscopy, X-ray diffraction crystallography, Raman, UV-Visible absorption, BET surface area measurement and photoluminescence spectroscopy. In addition, their photocatalytic activities for methyl orange were tested under irradiation by visible light. The BET surface area, adsorption and photocatalytic activity occurred in the order AgBr/BiOBr < BiOBr << Bi0Br(x)I(1-x) (x = 0.3, 0.5 and 0.7). The flower-like BiOBr microspheres exhibited a band gap of 2.76 eV, which decreased with increasing I/Br ratio. The O-center dot(2)- and h(+) were found to be major active species for MO degradation. For BiOBr and AgSr/BiOBr microspheres, (OH)-O-center dot radical formation was clearly observed, while the role of (OH)-O-center dot radical was found to be negligible for BiOBrxI1-x (x = 0.3, 0.5 and 0.7) microspheres.