Density Functional Study Adsorption Of Small Molecules On MgO (001) Surface And The Surface Supported Sodium Monolayers

Due to its relevant importance in a variety of processes, such as catalysis, photo-electrolysis, electronic-device fabrication, prevention of corrosion, and sensor development, the adsorption on metal oxide surfaces has been an active research area. At present, the studies mainly concern the thermo-dynamical adsorption on perfect metal oxide surfaces. However, the adsorption on defect surfaces and the adsorptive reaction mechanism on the aspect of kinetics, which is a hot research field in solid-state quantum chemistry, are relatively in lack. MgO is a typical metal oxide with simple rock-salt structure and high stability in structure. In this dissertation, the adsorption and catalytic dissociation mechanism of some small molecules on MgO (001) defect surfaces has been investigated. The main study contents are as the following: 一,The adsorption of CO on MgO (001) surface, a paradigmatic case, is studied. It was found that a more reasonable surrounding environment for cluster models can be obtained when the value of embedded point charges is determined by charge self-consistent technique. The calculated surface relaxation, CO adsorption energies as well as CO frequency shift are all in good agreement with the latest experimental data. By the similar technique, the adsorption and dissociation of O2 on MgO (001) regular and defect surfaces is first systematically calculated. We found that the low-coordinated corner site and oxygen vacancies of MgO (001) surface in particular contributes to the dissociation of O2. 二,The adsorption and dissociation of Cl2 on MgO (001) surface supported Na monolayers is investigated. The calculated results indicate it is an effective catalyst toward Cl2 adsorption and dissociation. The role of substrate is not passive, which is different from CO adsorption on MgO (001) surface supported Na monolayers. A few electrons of Mg 3s orbital are transferred to the adsorbate, for Cl2 adsorption on MgO(001) surface supported Na monolayers. Based on the analysis of energy band and projected density orbital states, a "super-exchange" phenomenon is suggested and interpreted reasonably.三,In the last, we move to study the adsorption and dissociation mechanism of N2O at regular and defect sites of MgO (001) surface where it is interesting to find that N2O can be conversed into N2 at oxygen vacancy site with no energy barrier. In analogy, at oxygen vacancy site, NO can be spontaneously conversed into N2O. Therefore, we suggest that MgO with oxygen vacancies may be used as the good candidate for the prevention of NO pollution. These studied results have been not reported in the literatures.