275426 Poisoning Mechanisms of MgO-Supported Au Clusters in CO Oxidation

Monday, October 29, 2012: 1:50 PM
318 (Convention Center )
Giannis Mpourmpakis1, Michail Stamatakis2, Nima Nikbin2, Matthew A. Christiansen2 and Dionisios G. Vlachos3, (1)Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, (2)Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, (3)Catalysis Center for Energy Innovation, Chemical and Biomolecular Engineering, University of Delaware, Newark, DE

We investigated the CO oxidation mechanism on MgO-supported, subnanometer Au catalysts (Au6, Au8 and Au10), through multiscale modeling that combines density functional theory calculations with kinetic Monte Carlo simulations. For the case of Au6, our work unravels multiple catalyst deactivation mechanisms that depend on the type of the support vacancies. In defect-poor MgO or in the presence of a Mg-vacancy, O2 interacts weakly with Au6 and poisoning occurs by CO. On Au6 clusters that interact with an O vacancy of the support, O2 can be chemisorbed and some activity is observed. However, eventually, the Au6 cluster is poisoned by carbonate. For the similar case of negatively charged Au8 and Au10 clusters the carbonate formed was shown to decompose through pathways that result in CO2 production. Thus, these three different clusters were shown to exhibit different activity towards the CO oxidation reaction. This study underscores the importance of a cluster’s charge state on the catalytic activity and explains several experimental observations regarding the variable activity of metal-oxide supported Au nanoclusters.

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See more of this Session: Computational Catalysis I
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