|Site-directed Chemistry at Nanostructured Pt-Sn Alloys and Sn-Oxide Films on Pt.
Laboratory for Surface Modification
|Prof. Bruce Koel of University of Southern California
12pm in Room 260, Wright Rieman Chemistry Laboratory
Abstract: Achieving highest selectivity in heterogeneous catalysis, electrocatalysis, and sensing applications requires advances in understanding and control of structure and chemistry relevant to interfacial reactions at the nanoscale. STM is a powerful tool for obtaining such information, and when used in combination with complementary electron and ion spectroscopic techniques, one can obtain unprecedented information about how composition, structure, and defects alter chemical reactions that occur at specific sites at solid surfaces. We illustrate this "site-directed" chemistry by discussing a wide range of chemisorption and catalytic reactivity studies that have been used to establish new structure-property and structure-reactivity correlations on several Sn/Pt(111) and Sn/Pt(100) ordered surface alloys and ordered surface phases of SnOx films that can be formed by oxidation of these alloys. We describe the thermal stability of SnOx nanostructures and conditions for the formation of self-organized, molecular-sized, hexagonally ordered SnOx "nanodot" superlattices on Pt(111), and the growth of large-scale, oriented single crystals of SnO2 on reduced SnOx wetting layers on Pt(111). These studies were carried out on single-crystal surfaces in ultrahigh vacuum in order to provide simple model systems that are relevant to elementary processes occurring at more complicated, "technical" interfaces and well-defined surfaces that can be used to gather basic data needed to benchmark theoretical calculations. We reveal new insight into the nature of reactive sites at bimetallic and oxide-metal interfaces.