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

Abstract

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 (0) 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 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.