(689a) Relating Local Coordination to Function for Oxide Supported Pt Atoms

There is significant interest in atomically dispersed Pt-group metal catalysts supported on oxides. This interest stems from their efficient metal utilization, unique catalytic properties, and the potential for producing well-defined single-sites for fundamental catalytic studies. However, understanding of the properties of isolated metal atom active sites is complicated by the lack of information about the local coordination of the metal atom to the oxide, the homogeneity of the binding location of the metal atom to the support, and difficulties associated with differentiating single atoms from very small clusters in many characterization approaches. Here we demonstrate methods to unambiguously synthesize and characterize isolated Pt atoms on a range of oxide supports (TiO₂, CeO₂, Al₂O₃) with homogeneity in the local coordination environment of the metal atom bonding to the support. We establish how the properties of the support influence the preferred local coordination of the Pt atom. The local coordination is shown to dictate the stability of the Pt in atomically dispersed form, and its reactivity toward gas phase species. Finally, we show how exposure to different reactive conditions can lead to the structural evolution of these isolated sites. Together these contributions lead to a deeper understanding of the catalytic reactivity of supported metals at the atomic scale limit.