Preparation, characterization and photocatalytic activity of the neodymium-doped TiO2 nanotubes

A series of Nd-TiO2 powders have been prepared by the sol-gel technique with neodymium nitrate and tetra-n-butyl titanium as raw materials, and then Nd-TiO2 nanotubes were fabricated by the hydrothermal method with a 10 mol l−1 NaOH solution. The as-prepared Nd-TiO2 nanotubes were characterized by TEM, XRD, DRS, and XPS, and their photocatalytic activity was also tested in the case of the degradation of methyl orange in water. TEM photograph showed that Nd-TiO2 nanotubes were about 10-20 nm in diameter, with the lengths range from 100 to 300 nm. TiO2 nanotubes contained anatase and rutile crystallites. However, 0.3% Nd-TiO2 nanotubes contained anatase crystallites, and only little rutile crystallites, so it is shown that neodymium doping hindered the phase transformation from anatase into rutile. Nd doping increased the visible-light absorption ability of Nd-TiO2 nanotubes, and a red shift for Nd-TiO2 nanotubes appeared when compared to TiO2 nanotubes. XPS analysis showed that two types of oxygen existed on the photocatalyst surface, including metal-O and hydroxyl group, and more hydroxyl group was on the surface of 2% Nd-TiO2 nanotubes than on the surface of TiO2 nanotubes. Nd doping enhanced the photocatalytic activities of Nd-TiO2 nanotubes, and 0.3% Nd-TiO2 nanotubes exhibited the highest photocatalytic activity.