Photoactive and adsorptive niobium-doped anatase (TiO2) nanoparticles: Influence of hydrothermal conditions on their morphology, structure, and properties

Anatase-type TiO2 nanoparticles with adsorptivity and improved photocatalytic activity for the decomposition of methylene blue (MB) in its aqueous solution, which contained up to 10 mol% niobium by forming solid solutions with niobium oxide, were directly synthesized from precursor solutions of TiOSO4 and NbCl5 under three hydrothermal conditions in the absence and presence of urea and aqueous ammonia at 180 degrees C for 5 h. The influence of the hydrothermal conditions on the crystallite growth, morphology, specific surface area, adsorptivity, and photocatalytic activity of niobium-doped TiO2 was investigated. The crystallite growth of anatase was enhanced by the presence of the niobium component. The 10 mol% niobium-doped TiO2 that was prepared under the hydrothermal condition in the presence of urea had fine crystallites (11 nm) and high specific surface areas (135 m(2)/g), which showed the most enhanced photocatalytic activity and the highest adsorptivity. The hydrothermal treatment under weak basic conditions and formation of solid solutions with niobium oxide brought about a considerable increase in the adsorption of MB for the anatase-type TiO2.