Preparation, Characterization And Photocatalytic Activities Of Titanium Dioxide With Two Dimension And Three Dimension Structures

In this study, surface-fluorinated anatase TiO2nanosheets with exposed{001} facets and TiO2containing anatase nanoparticles and rutile nanoflower structure consisting of nanorods were synthesized and the activities of the catalysts in the photocatalysis of Cr(VI) and methyl orange (MO) were investigated, respectively. The structure and properties of the resultant catalyst powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyzer.TiO2is widely used for the photocatalytic removal of various types of pollutants in water. In the present work, reduction of Cr(VI) induced by UV-visible light in aqueous solution was investigated. The aqueous medium contained TiO2nanosheets and no additional reducing agents or hole scavengers. A hydrothermal method was used to synthesize fluorinated TiO2nanostructures with various percentages of exposed{001} facets and initial F/Ti ratios. Fluorine-free TiO2nanosheets were obtained by washing the TiO2samples with NaOH solution. The role of the surface fluorination and the{001} facets in adsorption and photoreaction of Cr(VI) were elucidated by determining the saturated adsorption capacity and pseudo-first-order reaction rate constants of these processes. With the help of physicochemical measurements, we determined that the surface fluorination facilitate the adsorption process by increasing the number of surface OH groups generated. Moreover, fluorination efficiently inhibits the recombination of photogenerated electron-hole pairs. The{001} facets have an indirect role in the photocatalytic reduction of Cr(VI) because oxidative dissolution of H2O occurring on {001} facets and Cr(VI) reduction occurring on{101} facets are simultaneous reactions. The optimal ratio of exposed{001} to{101} was found to be-72:18.A series of TiO2with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium n-butoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activity of the samples was evaluated by degradation of methyl orange in aqueous solution under UV-visible light irradiation. On the basis of detailed analysis of the characterizing results of high-resolution transmission electron microscopy, X-ray powder diffraction measurements, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, it was concluded that the photo-activity of the catalyst is related directly to the3D morphology and the crystal phase composition. An excellent catalyst should have both a rutile3D flower-like structure and anatase granulous particles. The3D flower-like structure could enhance light harvesting, as well as the transfer of reactant molecules from bulk solution to the reactive sites on TiO2. In addition, the optimum anatase/rutile phase ratio was found to be approximately80:20, which is beneficial to the effective separation of the photogenerated electron-hole pairs.