Morphology And Structure Effects Of Ceria And Supported Copper Oxide Nanocatalyst On The Activity And Adsorption Behavior For NO Reduction

PartⅠ:The purpose of present work focused on exploring the influence of support structure on the activity and adsorption behavior of copper-based catalysts. The incorporated copper species on ceria (111) surface were in an unstable five-coordination structure, and on t-ZrO2 (111) surface in the elongated environment, whereas onγ-Al2O3 (110) surface were in a symmetrical and stable octahedral coordination. These dissimilarities naturally influenced the synergistic interaction between copper and supports, thus CuO/CeO2 catalyst showed the higher reducibility and activity for NO reduction. In situ FT-IR of NO adsorption/desorption results revealed that compared with those adsorbed species on CuO/t-ZrO2 and CuO/y-Al2O3, the bidentate and monodentate nitrates over the ceria-rich phase catalysts were more active to desorb or transform. Hyponitrites were identified on its surface above 100℃due to the formation of oxygen vacancy. Co-interaction of NO+CO results suggested that the adsorption type and reactivity of NOX species were dependent on the supports structure and temperature. The chelating nitro, bidentate and bridge nitrates over CuO/CeO2 surface were more active to react with CO at low temperatures due to its superior redox activity. PartⅡ:The present work comparatively explored the morphology and size-dependent reduction and activity of CeO2 nanostructures for NO reduction. CeO2 nanorods were prepared by Ce(NO3)3, while spherical-like nanoparticles with an average size of 4-6 nm were obtained from (NH4)2Ce(NO3)6 and Ce(SO4)2. As compared with CeO2 nanorods, these nanoparticles (4-6 nm) showed the larger lattice strain and higher activity for NO reduction, which was due to the nanosize effect that significantly improved the intrinsic reducibility of surface oxygen and facilitated the formation of oxygen vacancies. In addition, the adsorption type and configuration of NO was similar over these different shaped ceria. However, CeO2 nanoparticles from tetravalent cerium showed the greater capacity to activate the adsorbed NO species than nanorods from the tervalent nitrates.