Nanocomposite of Ag-AgBr-TiO2 as a photoactive and durable catalyst for degradation of volatile organic compounds in the gas phase

The nanocomposites of Ag-AgBr-TiO2 photocatalyst have been prepared by a simple deposition-precipitation method, which is used for the gas-phase degradation of volatile organic pollutants of aromatic benzene and non-aromatic acetone that are notorious volatile organic compounds (VOCs) present in indoor and outdoor air. A collection of joint techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet/visible diffuse reflectance spectra (UV/vis DRS) have been employed to determine the structure, morphology and optical properties of the as-prepared Ag-AgBr-TiO2 nanocomposite. The presence of surface Ag species existed as Ag (O) and Ag (I) in Ag-AgBr-TiO2 is confirmed by the analysis of X-ray photoelectron spectroscopy (XPS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O-Ti and O-Ti-O after the deposition of AgBr and Ag species onto the surface of TiO2. It is found that the Ag-AgBr-TiO2 nanocomposite exhibits much higher photocatalytic activity and stability under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the gas-phase degradation of both aromatic benzene and non-aromatic acetone. The active radical species involved for degradation reactions over the Ag-AgBr-TiO2 photocatalyst have been investigated by the spin-trapping electron paramagnetic resonance (EPR) spectra and the center dot OH-trapping photoluminescence (PL) spectra. Synergetic effects between Ag-AgBr and TiO2 have been observed and discussed for the gas-phase degradation of volatile organic compounds on the basis of joint results of characterization and photocatalytic activity. (C) 2011 Elsevier B.V. All rights reserved.