Preparation of vanadium-doped titanium dioxide neutral sol and its photocatalytic applications under UV light irradiation

A sol-gel method was used to prepare V-doped TiO₂ sol. TiCl₄ was converted to Ti(OH)₄ and H₂O₂ was then added to convert it to TiO₂ at high temperature. The sols with various contents of V were used to prepared thin films on glass substrate by dip-coating method. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy, and UV-vis spectroscopy. The photocatalytic activities of the V-TiO2 thin films were investigated by the degradation of methylene blue under UV light irradiation. The as-prepared V-TiO₂ sol was neutral and showed high stability of nanoparticles suspended in the sol without any surfactant. The shape of particle was rhombus and possessed high aspect ratio. The V-TiO₂ particles were in anatase and nanosize, so they do not need annealing process to form crystals after coating on the substrate. V doping can produce more photogenerated electrons and holes, which improved the photocatalytic activity. However, overdoes V in TiO₂ would lead to form the recombination centers and suppressed the activity. The optimum NH₄VO₃/TiO₂ weight ratio in starting materials was 3%.