Effects of indium doping on properties of xIn-0.1%Gd-TiO2 photocatalyst synthesized by sol-gel method

A sol-gel method was used to prepare a novel In-Gd co-doped TiO2 photocatalyst. The materials were characterized by XRD, SEM, FT-IR/FIR, UV-Vis diffuse reflectance, XPS, and N2 adsorption-desorption analyses. The diffraction patterns of all the materials belong to anatase phase TiO2 in tetragonal system. The doping of 0.1% Gd in the TiO2 metrix leads to a sharp reducing crystallite size, while the crystallite size decreases very slightly after the subsequent doping of indium. In3+ and Gd3+ ions are incorporated into the crystal lattice of anatase TiO2 by substituting Ti4+ ions. The main Ti-O bond is maintained in the TiO2 matrix and is not noticeable influenced by the dopants. Band gaps of the materials slightly decrease after doping. When indium content is less than 3%, both surface area and pore volume increase with rising indium content. The largest BET surface area of 122.7 m2/g is obtained in the 3%In-0.1%Gd-TiO2. The binding energies of titanium and oxygen in 0.1%Gd-TiO2 are nearly unchanged after doping of indium. The maximum photocatalytic activity is found on 3%In-0.1%Gd-TiO2. After 45 min of irradiation, more than 90% of methyl orange molecules are removed from the solution by 3%In-0.1%Gd-TiO2, while the efficiency is only 40% on the undoped TiO2.