DFT Study Of Molecules Adsorption And Reaction On TiO₂（110） And Graphene

With the development of computational methods and computer technology, the first-principles calculations have been widely used in condensed matter physics, materials, chemistry and so on. Because water is one of the most abundant compound on our planet, and its influence can permeate virtually all areas; it is essential to further understand the interaction mechanism between water molecules and solid surfaces, especially in many environment-and energy-related applications. Where the solar energy is one of inexhaustible clean energy, water splitting using light to convert solar energy into hydrogen is the ideal way to solve environmental issues and energy crisis, and it is of great significance and has a potential application. Therefore, the adsorption and activation of water on the surface of solid catalyst is one of important issues of concern.Titanium dioxide, due to its non-toxicity, good biocompatibility, chemical stability and excellent self-cleaning, has a wide application in solving the energy crisis and environmental pollution. Graphene, possessing a high surface area for the dispersion of metal nanoparticles and a good electrical conductivity required for electron transfer in catalysis, has been extensively studied in the photocatalysis. In this thesis, first-principles calculations were performed to investigate the adsorption and dissociation behaviors of H2O on the TiO2(110) surface and graphene modified by Ti atoms, and further elaborated the crucial role of N doped in graphene for catalysis. Our results provide fundamental insights into the microscopic mechanisms and assess the possibility of using as a catalyst.In chapter1, we introduced the rutile titanium dioxide and graphene, including structures, properties and preparation methods, and some of their research progress, especially in the adsorption and dissociation of water.In chapter2, we introduced some basic concepts and framework of density functional theory, then some softwares often used in DFT were introduced, At last, some analysis methods used in the thesis were introduced. In chapter3, the adsorption and dissociation of water molecules on TiO2(110) has been extensively explored, but the titanium adatom, can be seen both as one defect in titanium oxide and as a way of modifying with a metal atom, is less well-studied, so we focus on the effect of the Ti adatom on the adsorption and dissociation of water molecules. Our results pointed out the Ti3d played a key role, and the electron localization does not change the reaction mechanism.In chapter4, we performed DFT calculations to investigate the catalytic activity of Ti decorated graphene for H2O dissociation. The effects of vacancy and the way of Ti decoration were discussed, Vacancy in graphene can efficiently enhance the Ti adsorption, and the chemical reactivity of the Ti4cluster on graphene is substantially higher, leading to dissociation of adsorbed single H2O with almost no energy barrier, even the dissociative adsorption of the second water also appears. The result might provide insights into the potential applications in hydrogen production. Then, hydrogen tunneling through graphene sheet was studied to explore the permeability of a single graphene sheet. The results show the defect can greatly reduce the energy barrier, but not limited to the defect site itself, which has a certain influence region. The shape and size of the defect will also have some impact to a certain extent.In chapter5, the role of N doped in graphene for Pd catalyst was studied by combining experimental and DFT. It is found N atom can enhance the adsorption of Pd and increased the electron in Pd atom, promote the electrons transfer from support to substrate that protected C=O group and exclusively improved the C=C selectivity. So the N-atom doped graphene can improve the dispersion and catalytic activity of the supported Pd catalyst. The results agree well with experiment. The N-atom doped also decrease the spillover barrier of H from Pd to support, so it may increase the capacity when as the hydrogen storage material; further, in the whole catalytic system, N-atom doped makes the H transfer easier and it may lead to CALD hydrogenation ersier.