CO And NO In Automobile Exhaust Catalytic Elimination Of Experimental And Theoretical Research

Nanosheet and flower Ni (OH) 2 were synthesized by hydrothermal synthesis method, then corresponding NiO were obtained by calcined at 573 and 773 K. Using X-ray diffraction (XRD), scanning electron microscope (SEM), BET surface area, temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS), the structures and properties of NiO were systematically characterized. CO oxidation activity was tested for NiO samples with different morphologies. For NiO calcined at the same temperature, the surface area of nanosheet is larger than that of flower-like sample, which leads to more unsaturated Ni atoms and higher concentration of defects oxygen species. Correspondingly, the activity of CO oxidation for nanosheet NiO is higher than that for flower-like sample. For NiO samples with the same morphology, CO activity of NiO calcined at 573 K is higher than that calcined at 773 K for the BET surface area of the former is much larger than the latter. The possible oxidation mechanism for CO oxidation on NiO was explored on the basis of experimental results.The cubic nano ceria was prepared by hydrothermal synthesis method, then the corresponding Rh2O3/CeO2 catalysts were obtained by impregnation method with a mass fraction of 0.1%,0.5% and 1.0% Rh2O3. By using X-ray diffraction (XRD), transmission electron microscope (TEM) and BET surface area, the physical structures and properties of Rh2O3/CeO2 catalysts were systematically characterized. Meanwhile, the chemical properties and electronic information of Rh2O3/CeO2 catalysts were systematically obtained by H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). No diffraction peaks of were observed due to its low content and small nanoparticle size in XRD patterns, and the size of cubic nano-ceria is 40 nm. CO oxidation activity was tested for Rh2O3/CeO2 samples The results indicate that the CO oxidative activity of pure ceria is relatively low, while it is greatly improved with the increase of Rh2O3 loading. When Rh2O3 in catalysts is reduced to metal Rh, their CO oxidative activities are much higher than those before reduction. On the basis of experimental results,. the reaction behavior of CO oxidation on the different active sites of Rh2O3/CeO2 catalysts by density functional theory method. The theoretical results imply that the oxygen species at the interface between Rh2O3 and ceria, as well as O of Rh2O3 with low coordination have the relatively higher CO catalytic activity.Rh and its oxides are the most important active components of three-way catalysts for NOx elimination. Therefore, it is of great significance to investigate the NO reaction mechanism on Rh-based catalysts at an atomic level. Using density functional theory calculation, the adsorption and reaction behaviors of NO on Rh (111) were systematically investigated. The theoretical results indicate that the most stable configuration of NO locates at the hep hollow site of Rh (111), and its directive dissociation energy barrier is relatively high. When H coadsorbs with NO on Rh (111), the activation energies of the formation for NOH and HNO intermediates are also high. According to the DFT calculations, the possible dissociation path of NO is that NO at the hcp hollow site firstly transforms into the lying configuration, and then directly dissocates into N and O atoms.