Effect of Niobium on the Structure and Photoactivity of Anatase (TiO₂) Nanoparticles

Anatase-type TiO₂ nanoparticles doped with 0–30 mol% niobium were directly formed from precursor solutions of TiOSO₄ and NbCl₅ under mild hydrothermal conditions at 120–180 °C for 5 h using the hydrolysis of urea. When the niobium content increased from 0 to 30 mol%, the crystallite size of anatase increased from 8.5 to 19 nm. The band gap of anatase was slightly decreased by making solid solutions with niobium. Their photocatalytic activity and adsorptivity were evaluated separately by the measurement of the concentration of methylene blue (MB) remained in the solution after maintained in the dark or under UV-light irradiation. To form anatase-type solid solutions by doping 5–15 mol% niobium into TiO₂ was effective for improvement of the photoactivity of TiO₂. The photocatalytic activity (the photooxidation rate) and the adsorption amount of MB for the sample containing 15 mol% niobium became more than approximately nine times and six times as much as those of the hydrothermal anatase-type pure TiO₂, respectively.