Morphologic effects of nano CeO2–TiO2 on the performance of Au/CeO2–TiO2 catalysts in low-temperature CO oxidation

Abstract

CeO2–TiO2 composite nanorods and nanoparticles were synthesized by hydrothermal and co-precipitation methods, respectively; with the CeO2–TiO2 composite of different morphologies as supports, Au/CeO2–TiO2 catalysts were prepared by the colloidal deposition method and used in CO oxidation at ambient temperature. N2 sorption, XRD, HRTEM, H2-TPR, XPS and XAS characterizations were used to clarify the relationship between the morphologic properties of CeO2–TiO2 and the catalytic performance of Au/CeO2–TiO2. HRTEM results show that Au/CeO2–TiO2 nanorods are dominated by CeO2 nanocrystals with (110) and (100) facets, while the Au/CeO2–TiO2 nanoparticles mainly expose (111) planes. XPS and XAS results reveal that both Au/CeO2–TiO2 nanorods and Au/CeO2–TiO2 nanoparticles are similar in the state of gold species. H2-TPR results indicate that the presence of Au strongly promotes the reduction of CeO2 in the Au/CeO2–TiO2 nanorods. The catalytic activity of Au/CeO2–TiO2 in CO oxidation is strongly related to the morphology of CeO2–TiO2; the CeO2–TiO2 nanorods as support endow the Au/CeO2–TiO2 catalyst with much higher activity than the CeO2–TiO2 nanoparticles. The (110) and (100) facets of CeO2 dominated in the Au/CeO2–TiO2 nanorods are able to promote the oxygen migration and gold dispersion, which may then evidently enhance the redox capacity and catalytic activity of the Au/CeO2–TiO2 nanorods in CO oxidation at low temperature.