Fluxionality of Au Clusters at Ceria Surfaces during
CO Oxidation: Relationships among Reactivity, Size, Cohesion, and
Surface Defects from DFT Simulations
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Abstract
Density
functional theory (DFT) calculations are used to identify
correlations among reactivity, structural stability, cohesion, size,
and morphology of small Au clusters supported on stoichiometric and
defective CeO<sub>2</sub>(111) surfaces. Molecular adsorption significantly
affects the cluster morphology and in some cases induces cluster dissociation
into smaller particles and deactivation. We present a thermodynamic
rationalization of these effects and identify Au<sub>3</sub> as the
smallest stable nanoparticle that can sustain catalytic cycles for
CO oxidation without incurring structural/morphological changes that
jeopardize its reactivity. The proposed Mars van Krevelen reaction
pathway displays a low activation energy, which we explain in terms
of the cluster fluxionality and of labile CO<sub>2</sub> intermediates
at the Au/ceria interface. These findings shed light on the importance
of cluster dynamics during reaction and provide key guidelines for
engineering more efficient metal–oxide interfaces in catalysis