Energetics and Statistics of O2 Dissociation Over Pt(111) Surface at Finite Coverages

Tuesday, November 9, 2010: 2:36 PM
Grand Ballroom B (Hilton)
Chao Wu1, David Schmidt1, Christopher M. Wolverton2 and William F. Schneider1, (1)Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN, (2)McC Materials Science and Engineering, Northwestern University, Evanston, IL

O2 dissociation is a key step in many surface catalytic reactions involving oxidation. O2 dissociation over Pt(111) surface is known to be affected by the oxygen adatom (O*) coverage at the surface. The O* coverage not only influences the energetics of further O2 dissociative adsorption (i.e., molecular chemisorption energy, dissociation barrier and O* binding energy), but also determines the reaction site statistics (i.e., how many types of dissociation sites and their site densities). The total rate of O2 dissociation is modeled through a sum over the rates of all types of dissociation sites weighted by their corresponding site densities.

Here we take advantage of a Cluster-Expansion (embedded in a Grand Canonical Monte Carlo method) of O* on Face Centered Cubic sites of Pt(111) surface to efficiently predict O* configurations as a function of temperature and coverage. With the predicted configurations, we identify types of dissociation sites according to CE O* binding energy and retrieve site densities. We then use Density Functional Theory to study O2 dissociation rates at each type of site. Eventually, we can construct a model to predict reaction properties incorporating coverage effects, such as reaction order and apparent activation energy under various reaction conditions.

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See more of this Session: Computational Catalysis II
See more of this Group/Topical: Catalysis and Reaction Engineering Division