Influencing Factors And Mechanism Of Bismuth Tungstate Photocatalysis

Using photocatalysis to water treatment attracts much attention these years. TiO2is the most widely researched photocatalyst as it has high photocatalytic activity, low price and excellent stability. But TiO2can only absorb the UV light, which accounts for only a small part of the solar spectrum. It is necessary to develop a visible-light-driven photocatalyst. Although WO3is a visible-light-driven photocatalyst with high activity, it can’t use O2as eletron scavenger, which makes it’s costly to practical application. As a new visible-light-driven photocatalyst, Bi2WO6makes reseachers excited. As is reported, Bi2WO6can degrade organic pollutant in aerated aqueous solution using O2as electron scavenger. In this regard, Bi2WO6is worthy of being further studied as an environmental photocatalyst.In this work, flower-like Bi2WO6is chosen as the investigated catalyst. The research concentrates on the physical property, reaction activity and mechanism of Bi2WO6photocatalysis. The main contents and results are as follows:In the first part, flower-like Bi2WO6was synthesized by a modified hydrothermal method. The sample was sintered in air at different temperatures and the crystallinity, surface area, light absorption and microstructure caused by the sintering was invesitigated. Phenol was chosen as the substrate and its degradation over the different samples was determined. As the sintering temperature increased, the rate of phenol degradation first increased, and then decreased. The maximum rate of phenol degradation was the catalyst sintered at350℃, whatever the factor of surface area is considered or not. The comprehensive analysis of the physical property shows, the photocatalytic activity of Bi2WO6is determined by its crystalline structure, light absorption, and defect sites.In the second part, the Bi2WO6sample sintered at350℃was chosen as the investigated sample and the mechanism in the photocatalytic reaction was studied. WO3is chosen as a comparision when studied the mechanism, and phenol is also the substrate. The N,N-diethyl-p-phenylenediamine/peroxidase methed was used to determine the H2O2produced in the reaction and the electron paramagnetic resonance method was used to determined the·OH. The flat band potential was determined through the Mott-Schottky plot. The results show that in the photocatalytic reaction of Bi2WO6, the valence hole can oxidize H2O to produce·OH and the reduction of O2by conduction electron on Bi2WO6is a multi-electron process, to produce H2O2. As there are few photocatalysts capable of the multi-electron reduction of O2, Bi2WO6is a good visible-light-driven catalyst.