Influence of Ho3+/La3+-Doping on Photocatalytic Activity of TiO2 for Methyl Orange Degradation

The un-doped and Ho3+/La3+-doped TiO2 nanoparticles were prepared by sol-gel method with Ti (OC4H9)4 as raw material and characterized with X-ray diffraction (XRD) and UV-Vis absorption spectra (UV-Vis), and their photocatalytic activity were evaluated in the methyl orange (MO) degradation in aqueous suspension under UV irradiation. XRD shows that all samples preserve anatase structure. Ho3+/La3+-doping inhibites the increase of crystallite size, and leads to the lattice expansion and aberrance. A tiny blue-shift of the absorption profile in Ho3+-doped samples and a red-shift of the absorption profile in La3+-doped samples are found. Ho3+-doping and La3+-doping improve photocatalytic activity of TiO2 markedly. In the experiment condition, the optimum Ho3+ concentration is about 0.3% for the maximum photocatalytic degradation, and the optimum La3+ concentration is about 0.1%. The photocatalytic degradation efficiency of Ho3+-doping is almost equal to La3+-doping in their optimum doped concentration.