Photocatalytic properties of the transition metal doped TiO2 powder prepared by sol-gel process

초록

TiO2 is widely used as photocatalyst because of its optical and electronic properties, low cost, chemical stability and non-toxicity. Due to its band gap energy, TiO2 utilizes only a very small fraction of the solar spectrum and thus doping with metal ion has been employed to shift the light absorption to the visible region. In this study, transition metal doped TiO2 powder as a photocatalyst were prepared by sol-gel process using titanium isopropoxide as a Ti precursor. Sb, Bi and Nb were introduced as dopants, and the photocatalytic behaviors for the doped TiO2 powder were studied as a function of doping level and preparation conditions. X-ray diffraction, B.E.T. and scanning electron microscopy were applied for microstructural studies. Optical properties of the doped TiO2 powders were studied by UV-Visible-Spectrometer and photocatalytic activity of the doped TiO2 was characterized in terms of the degradation of a 1,4-dichlorobenzene. XRD analysis showed that doping with a transition metal ion suppresses anatase-to-rutile phase transition compared with the pure TiO2. The Sb, Nb-doped TiO2 powders did not exhibit any other diffraction peaks except TiO2. On the other hand, a diffraction peak of Bi4Ti3O12 appears for 5 at. % Bi-doped samples. All the doped TiO2 powders had higher specific surface area than that of undoped TiO2. Surface area increased with increasing dopant concentration depending on the dopant, from 33.9 m2/g to 55.4m2/g. The UV-visible absorption spectra of doped samples were red-shifted by 20~50nm according to doping level. Also transition metal doped TiO2 powders exhibited better photocatalytic active than the undoped TiO2.