Preparation of Fluorizated TiO2 Hollow Microspheres and Their Photocatalytic Activity

Using tetrabutyl orthotitanate as Ti source, hydrofluoric acid as F source and ethanol as solvent, well crystallized anatase-phase F-modified TiO2 hollow microspheres have, been synthesized via a solvothermal process. The structure and properties of the resulting samples were characterized by XRD, SEM, FTIR, XPS. The results indicated that the fluorizated TiO2 hollow microspheres had an anatase phase, the fluorine atoms were mainly distributed on the surface of TiO2, and existed in forms of chemical-adsorption. Hollow anatase TiO2 microspheres were achieved by Ostwald ripening under solvothermal conditions. Compared to pure titania, the fluorizated TiO2 hollow microspheres showed a much higher degradation efficiency, and degradation rate of which can be up to 98% during the photodegradation of methyl orange with the initial concentration of 20 mg.L-1 for 30 minutes. The mechanism for the great improvement for photocatalytic activity can be attributed to the unique structure of hollow microsphere and the fluorine modification, because the strong electron withdrawing ability of the surface Ti-F groups reduces the recombination of photogenerated electrons and holes, and enhances the formation of free OH radicals.