Influence of alumina, silica, and titania supports on the structure and CO oxidation activity of CexZr1-xO2 nanocomposite oxides

Nanocomposite oxides of CexZr1-xO2 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 Ce-9.33(SiO4)(6)O-2, 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 similar to 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 CexZr1-xO2 shows better performance, followed by TiO2- and SiO2- supported systems. The OSC properties of the supported CexZr1-xO2 oxides show a strong influence on the CO oxidation activity.