Photocatalytic degradation of methylene blue by Nd-doped titanium dioxide thin films

Abstract

In this work, Nd (0.5, 1.0, 1.5, and 2.0 at%)-doped TiO2 thin films were synthesized on Si (100) substrates using a sol–gel spin-coating technique. The formation of the anatase phase was demonstrated by X-ray diffraction and Raman spectroscopy. It was also demonstrated that the doping of the Nd element resulted in a TiO2 crystal structure. X-ray photoelectron spectroscopy proved that the doping of Nd element promoted the transfer of Ti4+ to Ti3+, which facilitates the photocatalytic performance of the TiO2 films. Scanning electron microscope and atomic force microscope demonstrated that all of the Nd-doped film surfaces showed different degrees of aggregation relative to the pure TiO2 film surface. It was verified that the doping of Nd altered the lattice structure of TiO2 thin films, resulting in lattice defects on the surface and changing the grain size of the films. Meanwhile, the lattice defects and changes in the chemical state affect the photocatalytic performance of TiO2 films, and the highest photoactivity was observed for an Nd doping concentration of 1.0 at%. Nd doping causes lattice defects conducive to the formation of more Ti3+ oxidation centers and reduces the photogenerated electron–hole recombination rate, resulting in the improved photocatalytic performance of TiO2 films.

Keywords

• tio2
• sol–gel
• photocatalytic activity
• nd doping