Density Functional Theory Study Of O And NO Adsorption On Au And Pt(111) Surfaces

The interaction of atoms and molecules with metallic surfaces is of great technological relevance. Understanding the atoms/molecules-surface interaction is one of the key issues for surface science and, in particular, for heterogeneous catalysis. The adsorption of gas atoms and molecules on transition metal surfaces is the first elementary step in a heterogeneous catalysis and it is fundamental to the understanding of catalytic mechanism. Nowadays it has being one of key subjects in the field of surface science and numerous studies have been carried out in experiments as well as theories. The first principles density function theory (DFT) calculation plays more and more important role in understanding of adsorption mechanics and explaining of experiment phenomenon in atomic scale.The thesis is dedicated to investigations the adsorption of gas atoms and molecules on metallic substrates, mainly including the adsorption properties of oxygen atoms on the Au (111) surface and NO molecules on the Pt (111) surface. For the O/Au (111) system, the adsorption energies, adsorption structures, work functions, density of electron and projected density of states have been calculated at different coverage. It has been found that the fcc hollow sites are the energetically favorable sites for all the coverage considered. The repulsive interaction has been identified, and the adsorption energy decreases with the coverageθ, while the work function increases linearly with the coverage. The O-Au interaction is very weak due to the fully occupied anti-bonding states from O 2p and Au 5d hybridization. The adsorption structure of NO/Pt (111) has been studied by calculating the Pt core-level shifts, which can be directly compared with high-resolution X-ray photoelectron spectroscopy. The results show that the NO species exist on the fcc-hollow sites not only at a low coverage of 0.25 Monolayer (ML) but also at high coverage of 0.5ML and 0.75ML. At the 0.25ML <θ≤0.5ML, the calculation indicates the on-top sites are also populated. Further more, the increasing of the coverage leads to the occupation of NO on the hcp hollow sites. It forms the p (2×2)-3NO structure with NO adsorption on the Fcc+Hcp+top sites at the saturation coverage of 0.75ML. The work provides an effective method which can be used to link experiment and theory result.