Size, Structure, Support, and Alloying Effects on Cluster Chemistry*

Size-selected model catalysts provide a useful tool for probing catalytic mechanisms, allowing observation of size-dependent correlations between cluster physical and chemical properties. Cluster deposition also allows preparation of model catalysts where the size and coverage of catalytic sites can be varied independently of each other, and of support structure. Size-selected clusters on well characterized supports are also amenable to detailed theory. Alloying catalytic nanoparticles provides an important tool for tuning adsorbate binding and catalytic properties, but extending mass-selected cluster deposition to bimetallic clusters is challenging. This talk will briefly describe an approach in which deposited size-selected clusters of a pure element (e.g. Pt) act as seeds for selective deposition of a second element (e.g. B or Sn). The activity of the clusters for several reactions under both gas-surface and electrochemical reaction conditions will be discussed.