Enhancement of the photocatalytic performance of Ag-modified TiO2 photocatalyst under visible light

A highly visible-light photocatalytic active Ag-modified TiO2 (Ag–TiO2) was prepared by a simple sol–gel process using TiOSO4 as the starting material, AgNO3 as a silver doping source, and hydrazine as a reducing agent. The prepared Ag–TiO2 samples were characterized by several techniques such as X-ray powder diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), energy dispersive X-ray spectrometry (EDX), X-ray absorption spectroscopy (XAS) and UV–vis diffuse reflectance spectroscopy (DRS). The Ag–TiO2 photocatalyst, a mixture of amorphous and anatase phases, has a high surface area. The silver contents in the Ag–TiO2 samples were determined by ICP measurements. The diffused reflectance UV–vis spectra indicated that the Ag–TiO2 samples exhibited higher red shifts compared with the undoped TiO2 sample. Indigo carmine degradation under visible irradiation indicated that the Ag–TiO2 catalyst gave higher photocatalytic efficiency than those of commercial P25-TiO2 and undoped-TiO2 samples. The Ag–TiO2 catalyst can be reused many times without any additional treatment.