Characterization of the thin layer photocatalysts TiO2 and V2O5- and Fe2O3- doped TiO2 prepared by the sol–gel method

Cam Loc Luu, Quoc Tuan Nguyen, Si Thoang Ho and Tri Nguyen

Abstract

The catalysts TiO₂ and TiO₂ doped with Fe and V were prepared using the sol–gel method. TiO₂-modified samples were obtained in the form of a thick film on pyrex glass sticks and tubes and were used as catalysts in the gas phase photo-oxidation of p-xylene. The physico-chemical characteristics of the catalysts were determined using the methods of Brunauer–Emmett–Teller adsorption, x-ray diffraction, and infrared, ultraviolet and visible and Raman spectroscopies. The experimental results show that the introduction of V did not expand the region of light absorption, but slightly reduced the size of the TiO₂ particles, and reduced the number of OH-groups, which should decrease the photocatalytic activity and efficiency of the obtained catalysts compared to those of pure TiO₂. The Fe-doped TiO₂ samples, in contrast, are characterized by an extension of the spectrum of photon absorption to the visible region with wavenumbers λ up to 464 nm and the values of their band gap energy decreased to lower quantities (up to 2.67 eV), therefore they should have higher catalytic activity and conversion efficiency of p-xylene in the visible region than the original sample. For these catalysts, a combined utilization of radiation by ultraviolet (λ = 365 nm) and visible (λ = 470 nm) light increased the activity and the yield in p-xylene conversion by a factor of around 2–3, as well as making these quantities more stable in comparison with those of TiO₂–P25 Degussa