Preparation And Properties Of Ceria And Gold Loaded Catalysts Nanomaterials With Different Morphology

1D、2D、3D cerium dioxide nanomaterials with different morphologies and properties were prepared mainly by hydrothermal method successfully, including:shortrods, longrods, cubic-plates, nanocubes, octahedra, polyhedra, nanospheres-like and so on. The morphology, structure, composition, optical property, crystal defects, oxygen vacancies, catalytic activity of the samples have been characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), ultraviolet-visible spectrum (UV-Vis), UV Raman spectroscopy (λex=325nm) and temperature-programmed reduction by hydrogen (H2-TPR), CO catalytic oxidation reaction as the model to study their activity. The main results are as follows:The one, two, three dimensional CeO2nanomaterials with different morphologies and nanostructures have been controllablly prepared by hydrothermal method. The results indicate that the crystallinity、dispersion and morphology of CeP2are the prerequisite to obtain high CO catalytic oxidation performance. In order to investigate the catalytic activity of CeO2shortrods, cubic-plates and spheres which have a better performance, CO catalytic oxidation as a model reaction. The results show that the CeO2nanospheres with particle size uniformity have a superior CO catalytic oxidation activity, the CO conversion around90%at365℃.We selecte three samples from one, two, three dimensional CeO2nanomaterials and high resolution electron microscopy studies have found that they expose the different crystalplanes. The results show that1D shortrods expose {110} and {100} planes,2D cubic-plates expose {110} plane and expose {100} plane in spheres. The CeO2spheres in the UV-Vis diffuse reflection show better absorption performance and are best in CO catalytic oxidation activity; shortrods CeO2have a large number of oxygen vacancies due to the strong reduction peak intensity in H2-TPR; cubic-plates CeO2with the largest average particle size have less crystal lattice defects which display lower CO catalytic activity.A series of Au/CeO2catalysts have been made based on shortrods、cubic-plates and nanospheres-like CeO2supporter, the CO catalytic oxidation reaction shows that shortrods structure exhibit more excellent catalytic activity. This is because {110} is active crystal which can stable Au+and adsorb CO molecules, meanwhile {100} crystal with large amounts of oxygen vacancies can provide oxygen. In a word, the coexist of {100} and {110} plays an key role in high CO catalytic oxidation. In addition, smaller nanometer gold particles is the key role to obtain a high catalytic activity. Neither {110} nor {100} dominate independently is favourable for high catalytic activity to the cubic-plates and nanospheres-like CeO2.CO catalytic oxidation shows that the different plane has a different effect on the stability and activity of gold particles. After doping Zr into carrier the morphology remains the same. When Au loaded, despite Zr4+substitute some Ce4+which helps in creating structural defects to enhance oxygen mobility on the {110} surface, but weakens the stability to gold. Au-O-Ce active sites decrease enormously and depress CO adsorbed concentration which lower Au/CeZrR and Au/CeZrS catalytic activity.