title: Textural, structural, and morphological characterizations and catalytic activity of nanosized CeO(2)-MO(x) (M=Mg(2+), Al(3+), Si(4+)) mixed oxides for CO oxidation.
abstract: The present work focuses on the combination of ceria with another oxide of different ionic valences from period 3 (Mg(2+), Al(3+), and Si(4+)) using coprecipitation method, followed by calcination at 450 and 750°C, respectively. The textural, structural, morphological and redox properties of nanosized ceria-magnesia, ceria-alumina and ceria-silica mixed oxides have been investigated by means of N(2) physisorption, XRD, Raman, HRTEM, DRS, FT-IR, and H(2)-TPR technologies. XRD results of these mixed oxides reveal that only nanocrystalline ceria (ca. 3-6nm for the 450°C calcined samples) could be observed. The grain size of ceria increases with the increasing calcination temperature from 450 to 750°C due to sintering effect. The highest specific surface area is obtained at CeO(2)-Al(2)O(3) mixed oxides when calcination temperature reaches 750°C. Raman spectra display the cubic fluorite structure of ceria and the existence of oxygen vacancies, and displacement of oxygen ions from their normal lattice positions in the ceria-based mixed oxides. DRS measurements confirm that the smaller the grain size of the ceria, the higher indirect band gap energy. H(2)-TPR results suggest that the reductions of surface and bulk oxygen of ceria were predominant at low and high calcination temperature, respectively. Finally, CO oxidation were performed over these ceria-based mixed oxides, and the combination of CeO(2)-Al(2)O(3) exhibited highest activity irrespective of calcination temperature, which may due to excellent textural/structural properties, good homogeneity, and redox abilities.
authors.affiliation: Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yu
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Wu
authors.forename: Changjin
authors.initials: C
authors.lastname: Tang
authors.forename: Lei
authors.initials: L
authors.lastname: Qi
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Keqin
authors.initials: K
authors.lastname: Sun
authors.forename: Lin
authors.initials: L
authors.lastname: Dong
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen