We will show that sub-nano surface-supported catalytic clusters covered with adsorbates generally have many low-energy isomers accessible at elevated temperatures of catalysis. The most stable isomers may not be the most catalytically active. Indeed, we will show how all practically-important properties of cluster catalysts, such as size- and composition-dependent activity, selectivity, and stability against deactivation, can be correctly modeled (i.e. in agreement with experiment) only as a dynamical statistical ensemble. A sub-ensemble of rare and metastable states furthermore dominates the catalytic properties. Additionally, states of the catalyst may interconvert with barriers of varying heights, in response to the changing adsorbates, i.e. exhibit fluxionality, during catalysts. Fluxionality is somewhat localized to regions of configuraitonal space where cluster structures are related. All these fundamental aspects are illustrated using dehydrogenation on deposited clusters of Pt, Cu, and Pd as the focus reaction.

Surface-mounted cluster catalysts: dynamic ensemble nature, and dominance of rare metastable sites in defining catalytic activity, selectivity, and durability

2019 Spring National Meeting

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