Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO_2 nanocrystalline

摘要

Sm~(3+)-doped TiO_2 nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm~(3+)-doped TiO_2 samples were tested for methylene blue (MB) decomposition and ~·OH radical formation. The analysis of ~·OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with ~·OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm~(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of ~·OH radical were simultaneously obtained for Sm~(3+)-doped TiO_2 nanocrystalline. The adsorption experimental demonstrated that Sm~(3+)-TiO_2 had a higher MB adsorption capacity than undoped TiO_2 and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of ~·OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm~(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of ~·OH radicals was, and thereby the highest photocatalytic activity was achieved.