AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA2
Photoemission of Adsorbed Xenon Studies on the Characterization of Reaction Sites on Oxygen-Modified Ni(110) Surfaces

Thursday, November 18, 2004, 2:20 pm, Room 210B

Session: Metal Oxides and Clusters IV: Oxide Surface Chemistry
Presenter: H. Guo, University of California at Riverside
Authors: H. Guo, University of California at Riverside
F. Zaera, University of California at Riverside
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Considerable attention has been paid in our laboratory to the study of the adsorption and reactions of surface intermediates of relevance to catalysis on clean, hydrogen- and oxygen-modified Ni(110) to understand the properties of these surfaces in hydrocarbon conversion, and in trying to identify specific sites selective for the promotion of desirable reactions. STM studies have evidenced that surface oxygen in lower coverage regimes not only induces reconstruction of Ni(110) in extending domains, but also modifies the electronic structure at local sites. Such surfaces have been found particularly effective in the production of heavier hydrocarbons. However, the relationship between this distinctive catalysis and the surface structures responsible for it cannot be established without a better knowledge of the local surface properties at the atomic scale. With this in mind, we have carried out experiments using photoemission of adsorbed xenon (PAX) to characterize specific adsorption sites in heterogeneous surfaces produced by oxygen adsorption on Ni(110) single crystals. This technique, which provides both energetic and local electronic information on small surface atom ensembles, has been used in combination with chemical titrations using probe molecules such as carbon monoxide and ammonia to determine correlations between electronic structures and reactivity. It was determined that ammonia prefers a direct interaction with the terminating atoms of the -Ni-O- added rows that form on Ni(110) upon oxygen treatments. Those sites appear to be key for the selective conversion of hydrocarbons.