The effect of electric transport properties of titanium dioxide nanostructures on their photocatalytic activity
Films formed by nanoparticles, nanorods and nanotubes of titanium dioxide with a thickness of 3.9, 4.0 and 4.1 gm, respectively, with an area of 2 cm2 were obtained by various methods. Nanostructures were characterized by X-ray phase analysis, scanning electron microscopy (SEM), BET (Brunauer-Emmett-Teller), BJH (Barrett-Joyner-Halenda). The electric transport properties of the films were studied by impedance spectroscopy. The photocatalytic activity of the samples was evaluated by the photocurrent and degradation of the methylene blue dye under xenon lamp illumination. The concentration of hydrogen released per unit time was determined by gas chromatography in a standard quartz cuvette using a platinum electrode. The study of texture characteristics showed that the obtained isotherms belong to type IV isotherms with a hysteresis loop, reflecting the process of capillary condensation in mesopores. The diffraction peaks for the films of nanoparticles and nanotubes of titanium dioxide are identical and correspond to the tetragonal phase of anatase, for films of nanorods to the tetragonal phase of rutile. When studying the electric transport properties of films, it was found that films of titanium dioxide nanoparticles have a higher resistance associated with unformed bonds between nanoparticles. Despite the low specific surface area, titanium dioxide nanorods showed higher photocatalytic activity than nanotubes and nanoparticles. The results are confirmed by measurements of photocurrent, dye decomposition and the splitting of water molecules into hydrogen gas and oxygen.