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 TiO 2 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 TiO 2 crystal structure. X-ray photoelectron spectroscopy proved that the doping of Nd element promoted the transfer of Ti 4+ to Ti 3+ , which facilitates the photocatalytic performance of the TiO 2 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 TiO 2 film surface. It was verified that the doping of Nd altered the lattice structure of TiO 2 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 TiO 2 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 Ti 3+ oxidation centers and reduces the photogenerated electron–hole recombination rate, resulting in the improved photocatalytic performance of TiO 2 films.