The Preparation And The Enhancement Methods For The Photocatalytic Of TiO₂ Thin Film On The Surface Of Glass

TiO2 photocatalysts have attracted a great deal of attention due to its promising environmental application in air purification, water disinfection, hazardous waste remediation, and water purification. However, the use of conventional powder catalysts results in disadvantages in recycle and separation, also producing pollution after the reaction. Preparation of the catalyst coated as thin film then has been a focus of attention. Soda lime glass is common and low in cost. High photoactive TiO2 thin film on the surface of soda line glass will make it have a widespread application in environment. However, it has found that sodium ions in TiO2 thin film diffused from the glass substrate during heat treatment have deleterious effects on the photocatalytic activity of TiO2- To develop new ecotypic building and environmental harmony materials and extend the use of the photocatalytic TiO2 thin films in the field of building materials, this thesis presents the preparation and the enhancement methods for the photocatalytic of TiO2 thin film on the surface of soda lime glass.TiO2 nanometer thin films were prepared on soda-lime glass and pre-coated SiO2 soda lime glass via sol-gel method, respectively. The as-calcined TiO2 nanometer thin films were men treated by dipping them in a 1 M HNO3 aqueous solution. The TiO2 nanometer films before and after surface acid treatment were characterized as follows: The morphology, grain size and crystalline phases of TiO2 thin films were investigated by using the scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The chemical composition and valency states of elements on the surface of TiO2 coating films were analyzed by X-Ray photoelectron spectroscopy (XPS). The transmittance and the absorption threshold of them were measured by UV-visible spectrophotometer. And photocatalytic activity of the thin films were evaluated by photocatalytic decoloration of methyl orange aqueous solution. The following results and conclusions are obtained. The photocatalytic activity of TiO2 thin films on soda lime glass is lower than that of TiO2 films on pre-coated with SiO2 coating. This is attributed to the fact that the sodium ions produce recombination centers of photo-generated electron-hole pairs on the surface and in the interior region of TiO2 particles, since the sodium and calcium ions easily diffuse from the soda lime glass substrate into TiO2 thin films during the heat treatment. That's to say that SiO2 layer can effectively retard thediffusion of Na ions from glass substrates to TiO2 films. The photocatalytic activity of TiO2 thin films was significantly enhanced after treated with HNO3 solution. The enhancement of the activity is ascribed to the reduction of sodium ions and the increase of the surface hydroxyl content in the TiO2 films.