Characteristics and photocatalytic behavior of Fe and Cu doped TiO2 prepared by combined sol-gel and mechanical alloying

In this paper, TiO2 gel was synthesized by the sol-gel method and then doped with Cu and Fe by mechanical alloying. Prepared photocatalysts were characterized throughout X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and ultraviolet-visible spectrophotometer. Photocatalytic behavior of prepared samples was studied by the degradation of methylene blue (MB) under both visible and ultra-violet (UV) region. XRD results indicated that phase structures of photocatalyst were the mixture of anatase and rutile phases. The content of the anatase phase increased to a maximum of 72 wt% in Fe doped TiO2 nanopowder. The agglomeration of Cu doped TiO2 particles was more severe than that of other samples. The average particle size of the Fe doped TiO2 samples was 120 nm smaller than that of the Cu doped sample. XRD, energy dispersive spectroscopy (EDS) and TEM results confirmed the more uniform dispersion and replacement of Ti by Fe in the TiO2 lattice structure. The results from DRS analysis obviously showed the shift of absorption band gap towards the visible region upon doping TiO2 with both Cu and Fe, with the minimum value of 2.8 eV for Fe doped TiO2. PL results showed that Fe doped sample had lower electron-hole recombination rate than other TiO2 samples. Degradation kinetics and the effect of initial MB concentration were studied by the Langmuir-Hinshelwood (L-H) model. In the case of Fe doped TiO2 photocatalyst, higher adsorption capacity and reaction rate constant were obtained. 2.5 wt% Fe doping is the optimal content for the degradation of phenol and MB dye.