Tuning the optical properties and photocatalytic activity of Ti_0.96Nd_0.02O₂ by Cd/Fe co-doping

This research work aims to investigate Fe/Nd and Cd/Nd co-doped TiO₂ thin films prepared by sol–gel and deposited by dip-coating onto soda-lime glass and the impact of these dopants on the photocatalytic properties. The structural, optical, morphological, and photocatalytic properties of all the prepared samples have been characterized by X-ray diffraction, atomic force microscope, UV–Vis spectroscopy (UV–Vis), and photoluminescence spectroscopy. Rietveld analysis of XRD patterns indicates that TiO₂ co-doping by Fe/Nd and Cd/Nd deteriorates the crystallinity of the pure anatase phase whereas the crystallite size seems not affected, i.e., 13 nm. The morphology of the surface has been affected; the roughness increases from 0.91 nm for pure TiO₂ to 2.73 nm for Cd/Nd co-doped TiO₂. UV–vis spectroscopy and photoluminescence analyses indicate that the band-gap energy decreases with co-doping from 3.33 eV for TiO₂ up to 3.26 eV for Fe-Nd/TiO₂. The degradation of methyl blue tests manifests that pure TiO₂ exhibits higher efficiency of 89% dye in three hours only. Significant decrease in the photocatalytic activity upon co-doping has been observed and a mechanism based on the combined effect of doping, annealing, and substrate effect is proposed to explain the photodegradation behavior.