Novel preparation method for a new visible light photocatalyst: mesoporous TiO2 supported Ag/AgBr

Abstract

A new method for the preparation of mesoporous TiO₂ with a surface deposited with nanoparticles of Ag and AgBr was developed. Cetyltrimethylammonium bromide (CTAB) was used as both a template agent and bromine source in the preparation process of the mesoporous TiO₂. Mesoporous TiO₂ containing CTAB was synthesized by a sol–gel method, and was dipped into AgNO₃ solution to form a mesoporous AgBr/TiO₂ nanocomposite. The AgBr/TiO₂ nanocomposite was irradiated by visible light to accelerate photolysis of AgBr, forming mesoporous Ag/AgBr/TiO₂ photocatalyst. The Ag/AgBr/TiO₂ photocatalyst was characterized by small angle X-ray diffraction (SAXRD), wide angle X-ray diffraction (WAXRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and N₂ isothermal adsorption–desorption. Ag/AgBr/TiO₂ exhibits high photocatalytic activity for the degradation of methyl orange under visible light irradiation. The photocatalytic reaction follows the first-order kinetics and the rate constant (k) for the degradation of methyl orange photocatalyzed by Ag/AgBr/TiO₂ is 63.6, 36.1 and 2.7 times that of mesoporous TiO₂ (M-TiO₂), commercial TiO₂ (P-25), and Ag/AgBr/SiO₂, respectively. The recycling runs experiment shows that the photocatalytic stability of the Ag/AgBr/TiO₂ photocatalyst is excellent. The visible light photocatalytic mechanism of Ag/AgBr/TiO₂ is also discussed.