Electronic Structure And Reactivity Of Metal Surfaces PDF Download

The ultimate goal in catalytic design is to have complete synthetic control of the material properties that determine the reactivity. Catalysts that consist of two metals (bimetallic) allow for potential greater reactivity and more flexible design. There are two factors that contribute to the modification of the electronic properties of a metal in a bimetallic surface: strain and ligand effects. Strain effects are due to a modified atomic arrangement of surface atoms in terms of distances and may include compressed or expanded lattices. Ligand effects are caused by chemical interaction of a metal atom with other metals in its vicinity. Having complete control of the electronic properties of a particular bimetallic surface, however, remains challenging. In this thesis, we have focused on using the strain and ligand effects to controllably tune the electronic structure of a metal surface and hence the metal-adsorbate chemical bond. We have investigated the electronic factor in the modified reactivity of epitaxially strained (Pt/Cu and Pt/Ag) and ligand modified (Pt-3d-Pt, 3d = Fe, Co, Ni) platinum surfaces towards the adsorption of oxygen. The electronic nature of chemisorbed oxygen on these surfaces was studied by probing occupied and unoccupied Pt-O states using synchrotron based x-ray emission spectroscopy (XES) and x-ray absorption spectroscopy (XAS), respectively. Using XES and XAS we are able to study the electronic states relevant for surface chemical bonding. For each surface structure studied, we observed significant perturbation in the valence electronic structure of adsorbed oxygen. Observed results are discussed within the framework of the d-band model -- a theoretical tool for predicting the adsorption properties of transition metal surfaces based on the average energy of the d-band.