The Preparation and Characterization of La Doped TiO2 Nanotubes and Their Photocatalytic Activity

La-doped TiO2 nanotubes (La/TiO2 NTs) were prepared by the combination of sol-gel process with hydrothermal treatment. The prepared samples were characterized by using transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectra, and ultraviolet-visible spectra. The photocatalytic performance of La/TiO2 NTs was studied by testing the degradation rate of methyl orange under ultraviolet (UV) irradiation. The results indicated La/TiO2 NTs calcined at 300 degrees C consisted of anatase as the unique phase. The absorption spectra of the La/TiO2 NTs showed a stronger absorption in the UV range and a slight red shift in the band gap transition than that of pure TiO2 nanotubes. The photocatalytic performance of TiO2 NTs could be improved by the doping of lanthanum ions, which is ascribed to several beneficial effects the formation of Ti-O-La bond and charge imbalance, existing of oxygen defects and Ti3+ species, stronger absorption in the UV range and a slight red shift in the band gap transition, as well as higher equilibrium dark adsorption of methyl orange. 0.75wt% La/TiO2 NTs had the best catalytic activity.