Study On Photocatalytic Performance Of Ag/AgBr/TiO₂ Nanocomposites

TiO₂-Gel and AgBr/TiO₂ nanoparticles were synthesized by sol-gel method and impregnation method, respectively, with TBOT, NaBr and AgNO3 as major raw material. Then Ag/AgBr/TiO₂ nanocomposites, which consist of silver nanoparticles deposited on AgBr surface, were prepared by photolysis reaction under visible light irradiation. Ag/AgBr/TiO₂ nanocomposites were characterized by means of X-ray diffraction （XRD）, UV-vis diffuse reflectance spectroscope （UV-vis DRS） , N2 isothermal adsorption-desorp- tion and high resolution transmission electron microscopy （HRTEM）. The results show that TiO₂ has homogeneous anatase phase, AgBr and Ag have face-centered cubic phase, respectively. The average diameter of the Ag/AgBr/TiO₂ nanocomposites is 13.58nm. The Ag/AgBr/TiO₂ nanocomposites have intense absorbtion in the whole visible light region. The photocatalytic activities and photocatalytic stability of Ag/AgBr/TiO₂ nanocomposites were researched by the degradation of methyl orange （MO）. The effects of photodegradation reaction conditions were studied too. The results show that theAg/AgBr/TiO₂ nanocomposites have relatively high photocatalytic activity and stability. The initial concentration of MO, catalyst dosage and pH of MO solution have certain effects on the photocatalytic activities of Ag/AgBr/TiO₂ nanocomposites. Ag/AgBr/TiO₂ nanocomposites were prepared by reverse microemulsion method. Factors affecting photocatalytic activities of Ag/AgBr/TiO₂ nanocomposites such as the molar ratios of Ti and Ag, the photolysis reaction time of AgBr and the calcinated temperature were investigated by the degradation of methyl orange aqueous solutions under visible light. The preparation conditions of Ag/AgBr/TiO₂ with high photocatalytic activities were confirmed that the molar ratios of Ti and Ag was 5?1, the photolysis reaction time of AgBr was 6h and the calcinated temperature was 450℃, respectively. Ag/AgBr/TiO₂ nanocomposites were characterized by X-ray diffraction （XRD） and UV-vis diffuse reflectance spectroscope （UV-vis DRS）. The results show that TiO₂ has anatase phase, AgBr has face-centered cubic phase and the average diameter of the Ag/AgBr/TiO₂ nanocomposites is 10.23 nm. The intense absorption of the Ag/AgBr/TiO₂ nanocomposites in the visible light area is attributed to the photosensitivity of AgBr. The results of photocatalytic degradation reaction of MO show that the Ag/AgBr/TiO₂ nanocomposites have outstanding visible light photocatalytic activities than the pure TiO₂. The recyling experiments of photocatalytic degration of methyl orange photocatalyzed by Ag/AgBr/TiO₂ nanocomposites under visble light irradiation were carried out. The result displays that the photocatalytic efficiency of MO slightly decreases with the recycling runs, and keeps almost constant after 3 successive cycles, which is still over 70% of that of the first recycling run, indicating that Ag/AgBr/TiO₂ nanocomposites possess good photocatalytic stability.