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In an effort to combine the favorable catalytic properties of Co3O4 and CeO2, nanocomposites with different phase distribution and Co3O4 loading were prepared and employed for CO oxidation. Synthesizing Co3O4‐modified CeO2 via three different sol‐gel based routes, each with 10.4 wt % Co3O4 loading, yielded three different nanocomposite morphologies: CeO2‐supported Co3O4 layers, intermixed oxides, and homogeneously dispersed Co. The reactivity of the resulting surface oxygen species towards CO were examined by temperature programmed reduction (CO‐TPR) and flow reactor kinetic tests. The first morphology exhibited the best performance due to its active Co3O4 surface layer, reducing the light‐off temperature of CeO2 by about 200 °C. In contrast, intermixed oxides and Co‐doped CeO2 suffered from lower dispersion and organic residues, respectively. The performance of Co3O4‐CeO2 nanocomposites was optimized by varying the Co3O4 loading, characterized by X‐ray diffraction (XRD) and N2 sorption (BET). The 16–65 wt % Co3O4−CeO2 catalysts approached the conversion of 1 wt % Pt/CeO2, rendering them interesting candidates for low‐temperature CO oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Precursor affected CeO 2 structure and the catalytic ability for imine synthesis. • CeO 2 from Ce(NO 3) 3 were better catalyst than those from Ce(OH) 4 and Ce(CH 3 COOH) 3. • Ethylene glycol coordinated differently with Ce precursor, H 2 O break these bonds. • Surface oxygen vacancies governed CeO 2 catalytic ability for imine synthesis. • Surface oxygen vacancies had more influences than the surface area and Ce3+ ratio. CeO 2 as catalysts for imine synthesis was synthesized from three different inorganic precursors (Ce(OH) 4 , Ce(COOCH 3) 3 ∙5H 2 O and Ce(NO 3) 3 ∙6H 2 O) in ethylene glycol (EG) as solvothermal solvent. The influences of some parameters were investigated, such as the surfactant polyvinylpyrrolidone (PVP), H 2 O as co-solvent, and CH 3 COOH or NaOH as mineralizer (exclusive for Ce(NO 3) 3 as the precursor). The different precursors influenced the coordination of EG with cerium, crystalline, surface structure and also the catalytic ability for imine synthesis. The highest imine conversion rate was obtained when CeO 2 was synthesized from Ce(NO 3) 3 + PVP + CH 3 COOH +EG. The mechanism was investigated by carefully checking the structures of the synthesized CeO 2 , such as XRD, morphology, surface area, XPS and so on, and figured out that the high catalytic activity of the best CeO 2 sample was much more related with the high proportion of surface oxygen vacancies than the surface area and the Ce3+ ratio. [ABSTRACT FROM AUTHOR]

Co3O4-modified CeO2 (Co/Ce 1:4) was prepared by a combination of sol-gel processing and solvothermal treatment. The distribution of Co was controlled by means of the synthesis protocol to yield three different morphologies, namely, Co3O4 nanoparticles located on the surface of CeO2 particles, coexistent Co3O4 and CeO2 nanoparticles, or Co oxide structures homogeneously distributed within CeO2. The effect of the different morphologies on the properties of Co3O4-CeO2 was investigated with regard to the crystallite phase(s), particle size, surface area, and catalytic activity for CO oxidation. The material with Co3O4 nanoparticles finely dispersed on the surface of CeO2 particles had the highest catalytic activity. [ABSTRACT FROM AUTHOR]