Adsorption and solar light activity of transition-metal doped TiO2 nanoparticles as semiconductor photocatalyst

Abstract

There is an eminent interest to improve the photoactivity of TiO2 nanostructures via doping with mid-band gap donors or acceptors to achieve a high solar absorption. In the present work, Cr- and V-doped TiO2 nanoparticles were prepared via a facile chemical vapor synthesis method. The effect of the transition metals (TM) on the solar light activity of the semiconductor nanoparticles as photocatalyst was examined by degradation of methylene blue and acid red 27. Induced coupled plasma and X-ray photoelectron spectroscopy analyses indicated high efficiency of the doping process in the hot wall reactor without surface covering of the TiO2 nanoparticles by the dopants. Diffuse reflectance spectroscopy also revealed a red shift of the absorption edge of the TiO2 nanoparticles with increasing dopant concentration. Analysis of the photoactivity of the synthesized nanoparticles under sun light showed an increase in the primary absorption of dye molecules on the surface of Cr- and V-doped TiO2 nanoparticles whereas the degradation rate was found to depend on the type and concentration of the dopants. A high photoactivity is obtained at 0.2 at% V concentration. The mechanism of photoactivity is discussed based on the effect of TM on the absorption edge of the semiconductor.