Preparation Of Silver, Nonmetal Modified Tytania And Its Enhanced Photocatalytic Activity

Two photocatalysts with enhanced photcatalytic activity were designed and successfully synthesized:(1) Ag-modified (B,P)-codoped TiO2hollow spheres and (2)(Ag, F)-modified anatase TiO2nanosheets with exposed (001) facets. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), Laser Raman spectroscopy (LRS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and their photocatalytic activities were evaluated by degradation of methylene blue (MB).The as-prepared samples exhibited high photocatalystic activity. Moreover,(Ag, F)-modified anatase TiO2nanosheets with exposed (001) facets expanded the photocatalystic activity to visible light region. The photocatalysis mechanism was discussed, and on base of the mechanism, the reasons why the catalytic activity was enhanced were further studied.As to Ag-modified (B,P)-codoped TiO2hollow spheres, the Ag particles on the surface of TiO2only play the role of photogenerated electron transmitter due to the good conductivity of metal Ag. Both the band-gap narrowing effect of nonmetal dopants and the photogenerate electron transmission effect of Ag0improved the photocatalytic activity of TiO2hollow spheres. In addition, the hollow sphere structure and oxygen vacancies were beneficial to the photocatalysis.As to (Ag, F)-modified anatase TiO2nanosheets with exposed (001) facets, Part of electrons transmitted from O to F through the F-Ti-O links because of the high electronegativity of F atom. There was strong interaction between the loaded Ag atoms and the unsaturated atoms on the exposed (001) facets. The strong interaction caused the absorbance edge red-shift of TiO2and the absorbance edge blue-shift of Ag. Under UV light irradiation, photoelectron-hole pairs were generated on the surface of TiO2. The photoelectrons were separated by Ag and F, which delayed the recombination of photoelectrons and holes. Thus the photocatalytic activity was enhanced. While under the irradiation of visible light, some of the photoelectrons transmit to the surface unsaturated atoms because of the strong interaction between Ag and unsaturated surface atoms, correspondingly, the holes were transmitted to the surface of TiO2. The holes and the formed hydroxyl radicals oxidize MB to CO2and H2O.