Preparation of silver-modified TiO2 via microwave-assisted method and its photocatalytic activity for toluene degradation

Silver-modified TiO2 (Ag-TiO2) with various Ag/Ti molar ratios were prepared by the microwave-assisted method and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS). Compared with the hydrothermal method, Ag-TiO2 of small crystallite size and high crystallinity can be obtained by the microwave-assisted preparation method. When the Ag/Ti molar ratio increased from 0 to 2%, the doping of Ag promoted the phase transformation and inhibited the growth of anatase crystallite. The absorption edge of Ag-TiO2 shifted to longer wavelength, and the band gap energy of Ag-TiO2 decreased. However, after increasing the molar ratio Ag/Ti further from 2 to 4%, the anatase content, the crystallite size and the band gap energy of Ag-TiO2 only increased slightly. In photodegradation gaseous toluene, the photocatalytic activity of Ag-TiO2 increased with the increase of Ag/Ti molar ratio from 0 to 1%, but declined with the further increase to 2%. The optimal Ag/Ti molar ratio for photocatalytic activity of Ag-TiO2 was found as 1%, with the content of anatase, rutile and brookite of 71.1, 14.5 and 14.4%, respectively. Compared with TiO2, Ag-TiO2 exhibited a better photostability in toluene degradation.