Preparation Of N And Sn Co-doped TiO₂ Film And Its Photocatalysic Activity In Range Of Visible Light

Photocatalysis TiO₂ has revealed very attractive application in the area of air pollution control,waste water treatment,bacillus resistance, pollution elimination,mist prevention and self-cleaning,still few studies were done under weak light source.In this study,N-or/and Sn-doped TiO₂ thin films(N/TiO₂,Sn/TiO₂,N/Sn/TiO₂)were prepared on glass slide by doping techniques based on sol-gel method,and their photocatalysic activity were evaluated by photooxidative degradation of formaldehyde using LED arrays as light source.The results showed that the photocatalytic activity of N/Sn/TiO₂ thin film was higher than that of undoped TiO₂ film,as well as that of N/TiO₂ and Sn/TiO₂ films.The crystal structure,surface properties and bandgap of these catalysts were investigated by X-ray photoelectron spectroscopy (XPS),scanning electron microscopy(SEM),X-ray diffraction(XRD), Raman spectra(Raman),infrared sectra(IR),Ultraviolet-Visible spectrophotomery(UV-Vis)and other analytic methods.Based on the characterization of structure and surface properties,the mechanism of ion-doping and the reason of higher avtivity were studied.Parts of tin ions entered into the lattices of TiO₂ and substituted titanium ions,a few of nitrogen ions formed a new kind of N-Ti bond.The new energy levels caused by doping exist inside of band gap of TiO₂,which induces absorption at longer wavelength and more effective in disparation of photo-induced electron-hole pairs.As a result,N/Sn/TiO₂ thin film shew high photocatalysic acitivity in range of visible light.In this thesis,the degradation process of formaldehyde was monitored On-line by means of gas chromatography.On the basis of it we analyse the mechanism of gaseous photocatalytic oxidation of formaldehyde.