Synthesis and characterization of nanostructured ceria-titania for photocatalytic applications

Abstract

Despite of the huge number of applications of titania (TiO2), a no-toxic, low cost and very promising photocatalyst, there are some critical factors that limit its photoactivity, first of all the fact that titania is a semiconductor only active in the UV region of the light spectrum. Several methods have been proposed to reduce its energy-gap value, among which noble metal deposition, surface modifications and doping with transition metal ions or rare earth elements Ceria (CeO2) has attracted great attentions due to its unique properties, such as biocompatibility, chemical inertness and strong oxidizing capability related to the formation of oxygen defects. CeO2-TiO2 systems seem to exhibit improved photocatalytic activity due to the enhanced mobility of excitons and/or reduced band gaps. In the present dissertation, nanostructured TiO2 samples containing different CeO2 loadings were synthesized and characterized by many techniques. Surface and bulk chemistry was evaluated by using X-ray powder diffraction (XRPD), X-ray photoelectron Spectroscopy (XPS) and infrared spectroscopy (DRIFT-IR); morphological and textural characterization was carried out by high resolution transmission electron microscopy (HRTEM); porosity was measured by N2 physisorption and the optical properties were studied by UV-vis spectroscopy (DRIFT UV-vis). Finally the samples were tested in the photodegradation of methylene blue (MB) in aqueous suspension under UV light.The CeO2-TiO2 nanostructured photocatalysts were found active in the test reaction attaining very high MB degradation values of dye oxidation after the monitored reaction period (120 min), with cerium-doped TiO2 (CeO2 loading less than 2.5 wt%) nanomaterials displaying a MB degradation rate higher than that of pure TiO2.