281737 Establishing the Connection Between the Geometric and Electronic Structure of Oxygen Species On Stepped Ag Surfaces: First-Principles DFT and Monte Carlo Studies

Wednesday, October 31, 2012
Hall B (Convention Center )
Matthew Morabito1, Hongliang Xin2 and Suljo Linic1, (1)Chemical Engineering, University of Michigan, Ann Arbor, MI, (2)Department of Chemical Engineering, University of Michigan, Ann Arbor, MI

Surface adsorbed species with different physicochemical properties, determined by local geometric and electronic structures, often have distinct reactivity toward chemical transformations. For example it has been shown that during ethylene epoxidation reaction electrophilic oxygen species on silver are responsible for the formation of ethylene oxide while the nucleophilic oxygen mainly leads to total combustion. Although much work has been done on identifying the electronic fingerprint of surface adsorbed species, the link between geometric and electronic structure of those species is still lacking.
Our objective is to establish the connection between the geometric and electronic structure of oxygen species on Ag surfaces (flat or stepped) under relevant catalytic conditions. The electronic structure (e.g., core-level shift) of different oxygen species has been probed using density functional theory (DFT) calculations. Using different approximations, we found that the final-state effect played an important role in determining the core-level shift of different oxygen species. We have also employed an atomistic thermodynamics approach and Monte Carlo simulations to extend the results of DFT calculations to relevant catalytic conditions (T, p). To ensure the complete sampling of the large space of possible surface configurations we have used the cluster expansion method to systematically coarse-grain the DFT-calculated energies. The developed computational framework can be readily applicable to study any reacting system where adsorbate-adsorbate interactions play an important role in determining the local geometric and electronic structure of adsorbed species.

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