Study of structural, spectroscopic and photo-oxidation properties of in-situ synthesized Sc-doped titania

A semiconducting composite with enhanced photocatalytic properties - scandium doped titania (anatase/amorphous titania/brookite) - was prepared by hydrolysis of titanium (IV) tetrabutoxide in the presence of scandium (III) sulfate aqueous solution. The characterization of the final products was accomplished through X-ray diffraction (XRD), scanning and high resolution transmission electron microscopy (SEM, HRTEM), UV-visible spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS) and by registration of photocatalytic activity during photo oxidation of aromatic organic compound (hydroquinone). The Sc-doped powder-like product is a mixture of anatase/brookite or anatase/brookite/amorphous nanoparticles. The effects of Sc-doping on the phase composition, optical properties and photoactivity of TiO2 were investigated. The XRD analysis confirmed the absence of individual Sc-containing compounds. The phase composition and particle size of TiO2 were characterized by the Debye analysis of X-ray diffraction patterns. A direct correlation between Sc concentration and TiO2 phase composition was established: increasing in Sc concentration promotes amorphization of the samples. DFT calculations distinguish both brookite and amorphous titania among all TiO2 polymorphs as the most preferred hosts for substitutional Sc atoms. In full accordance with TEM observations the possible inclusion of Sc into a TiO2 lattice is primarily gainful for amorphization. Both experimental and theoretical absorbance spectra for amorphous titania demonstrate a shift of absorbance onset towards larger wavelengths. An improvement in the catalyst's photodegradation efficiency was attained with Sc concentration of 5.0 mol%. (C) 2019 Elsevier B.V. All rights reserved.