Structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts have been investigated using X-ray diffraction (XRD), Raman spectroscopy, BET surface area, thermogravimetry, and high-resolution transmission electron microscopy (HREM). The effect of support oxides on the crystal modification of ceria cubic lattice was mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahighly dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO(2)-SiO(2) sample primarily consists of nanocrystalline CeO(2) on the amorphous SiO(2) surface. Both crystalline CeO(2) and TiO(2) anatase phases were noted in the case of CeO(2)-TiO(2) sample. Formation of cubic Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) (at 1073 K) were observed in the case of the CeO(2)-ZrO(2) sample. Raman measurements disclose the fluorite structure of ceria and the presence of oxygen vacancies/Ce(3+). The HREM results reveal well-dispersed CeO(2) nanocrystals over the amorphous SiO(2) matrix in the cases of CeO(2)-SiO(2), isolated CeO(2), and TiO(2) (anatase) nanocrystals, some overlapping regions in the case of CeO(2)-TiO(2), and nanosized CeO(2) and Ce-Zr oxides in the case of CeO(2)-ZrO(2) sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO(2) is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of the mixed oxide systems is more than that of pure CeO(2) and is system dependent.

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Nanocomposite oxides of Ce x Zr1- x O2 dispersed over alumina (Al2O3), silica (SiO2), and titania (TiO2) have been synthesized by a deposition coprecipitation method. The physicochemical characterization was carried out by X-ray diffraction (XRD), Raman spectroscopy, high-resolution electron microscopy (HREM), and Brunauer−Emmett−Teller (BET) surface area techniques. The catalytic efficiency toward CO oxidation was investigated under normal atmospheric pressure. Oxygen storage capacity (OSC) of the dispersed nano-oxides was also evaluated and correlated with the structural characterization and CO oxidation activity results. XRD measurements reveal the presence of dispersed cubic Ce0.75Zr0.25O2 nano-oxide phase over all the supports and the absence of unwanted inert compounds such as Ce9.33(SiO4)6O2, ZrSiO4, ZrTiO4, CeAlO3, and Ce−Ti oxides. Raman spectroscopy studies suggest formation of oxygen vacancies, lattice defects, and oxygen ions displacement from the ideal ceria cubic lattice positions. The HREM results indicate well-dispersed cubic Ce−Zr composite oxides of the size ∼5 nm over the surface of various supports. The CO oxidation activity results and the OSC measurements reveal the same order of efficiency:  that Al2O3-supported Ce x Zr1- x O2 shows better performance, followed by TiO2- and SiO2- supported systems. The OSC properties of the supported Ce x Zr1- x O2 oxides show a strong influence on the CO oxidation activity.