| The physical and chemical composition and the order of the atoms of solid surfaces are different from that of the bulk. Due to no atoms on the outer edge of the surface and forming "dangling bonds", the surface has active properties. In addition, the internal three-dimensional periodic potential field interrupts on the surface, so the electronic structures are also different from the bulk. These differences lead to the special properties of the surface. In the field of catalysis, the atoms on the surface are of high chemical reactivity. Molecules could be adsorbed on the surface and dissociate under proper conditions. The studies of surfaces give insight into the interactions between molecules and improve the understanding of catalytic mechanism. It could help researchers to improve the properties of the surface and guide researchers to design surfaces of special function.Metals and metal oxides play important roles in the field of heterogeneous catalysis. Among the metal oxides, the titanium oxide is considered as the promising catalytic and photocatalytic material. It is widely used in many fields, such as the fields of energy and environment. In the experimental and theoretical studies, the titanium oxide is commonly used as the model of transition metal oxides. Researchers hope that these studies could give insight into the metal oxide surface, which would help to improve the properties of materials and design new catalytic materials. In this thesis, density functional theory (DFT) calculations were performed to study the interactions between the defective TiO2(110) surface with bridging oxygen-vacancy pairs and the methanol molecule. In the following, the interactions between the defective TiO2(110) surface with two bridging-oxygen vacancies of two different array and the water molecule were studied. We explore the adsorption behaviors on different sites and the dissociation mechanism. Finally, we focus on the interactions between the TiO-terminated SrTiO3(110) surface and alcohols with different pKa values, to explore the roles of alcohols in the growth of SrTiO3nanocrystals. In chapter1, we introduced the geometric and electronic structures of the bulk and (110) surface of TiO2. Then we summarized the research progress of the adsorbed behaviors of molecules on the TiO2(110) surface, mainly about water and alcohol molecules.In chapter2, we firstly introduced some basic concepts and framework of DFT. Then some softwares often used in DFT were introduced. Thirdly, the testing of calculations was shown.In chapter3, we focused on the interactions between the defective TiO2(110) surface with bridging oxygen-vacancy pairs (OVP) and the methanol molecule. Results show that the OVP site is the most stable site for methanol adsorption, whether in molecular adsorption or dissociated adsorption. But the OVP site is not the most active site for dissociation. In addition, the OVP defect does not have significantly different influence on the adsorption structure and dissociation process of adsorbed methanol on5-fold Ti atoms at diverse positions:close to the vacancy or a little further from the vacancy. Methanol tends to adsorb molecularly on5-fold Ti atoms.In chapter4, we studied the defective rutile TiO2(110) surfaces with OVP and two next nearest neighbored bridging-oxygen vacancies belonging to the same row (NNN-OVs) using one water molecule as the probe. Results show the NNN-OV site is the most favorable site for water adsorption of two modes-molecular and dissociated adsorption, especially for dissociated adsorption. The dissociation energy barrier on NNN-OVs is a little lower than that on OVP. The5-fold Ti sites show similar behaviors despite the existence of different defects. Adsorption on this site is least stable and molecular adsorption is favored.In chapter5, the interactions between the TiO-terminated SrTiO3(110) surface and alcohols with different pKa values were studied. The water molecule, methanol molecule and the ethylene glycol molecule were chosen as three typical molecules. The results indicated that the adsorption energy of alcohol molecules on SrTiO3(110) surface is enhanced with the pKa value of alcohols reduced. It implied that the enhanced relative interaction strength between SrTiO3(110) surface and alcohol molecules would make the surface more stable. As a result, the surface area of SrTiO3(110) suface would expose more. The ratio of SrTiO3(110) surface in the SrTiO3nanocrystal would be added. |
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