Ultrasonic synthesis and photocatalytic performance of metal-ions doped TiO2 catalysts under solar light irradiation

Eight metal-ions doped TiO2 (M-TiO2) were successfully synthesized by an ultrasonic method, including Fe, Co, Ce, Cr, Mn, Mg, Ni and Ag ions. Among them, the 1% Mg-TiO2 shows the highest photocatalytic efficiency under solar light, which was determined by degrading rhodamine B (RhB) molecules in an aqueous solution. The synthesized M-TiO2 samples were characterized by XRD, BET Surface area, TEM, XPS and diffuse reflectance spectrum. Effects of synthesis conditions and characterized properties on photocatalytic efficiency of the M-TiO2 were investigated comprehensively. A positive correlation between specific surface area and photocatalytic efficiency of the M-TiO2 was found across different synthesis conditions. However, no clear correlation with photocatalytic efficiency was observed for crystal structure and radii of doping ions of the M-TiO2. XPS study indicates the change of oxidation states of Mn ions in Mn-TiO2 during synthesis procedure from the initial Mn2+ to a mixture of Mn3+ and Me4+ ions. Dye gensitization mechanism was observed during the photocatalytic procedure of the Mg-TiO2, which enhanced the degradation efficiency of the Mg-TiO2 under solar light. Finally, no obvious loss of photocatalytic activity was observed for the Mg-TiO2 after five cycles of RhB degradation. (C) 2012 Elsevier Ltd. All rights reserved.