Preparation and physicochemical properties of ZrO2 and Fe/ZrO2 prepared by a sol-gel technique

Pure ZrO2 and 0.5-5 wt % iron-containing samples have been prepared by a sol-gel technique and thoroughly characterized by several techniques, X-ray diffraction (XRD), differential thermal analyses (DTA), diffuse reflectance spectroscopy (DRS), scanning and transmission electron microscopies (SEM and TEM), X-ray photoelectron spectroscopy (XPS), and other complementary techniques. Introduction of iron in zirconia produced a phase transition from monoclinic to tetragonal. In contrast to generally reported values of zirconia band gap (5 eV), the values of the present samples ranged between 2.3 and 3.8 eV, determined from DRS,depending on the preparation conditions and on the iron content. Preliminary experiments of adsorption of different species (nitrite, ethylenediaminetetraacetic acid (EDTA), and Cr(VI)) are also presented and the results explained by a correlation with the physicochemical properties of the characterized oxides. Oxygen photoadsorption and oxygen isotopic exchange (OIE) results can be corelated to the photocatalytic activity recently found, showing the potentiality of this technique for the characterization of photocatalysts in order to account for its photoactivity.