Direct Imaging of the Atomic Configuration of Ultradispersed Catalysts

Direct imaging of individual catalyst metal atoms on the insulating surface of an industrial support is demonstrated. Individual platinum and rhodium atoms ultradispersed on γ-Al 2 O 3 supports were imaged by high-resolution Z -contrast (atomic number Z ) microscopy in a 300-kilovolt scanning transmission electron microscope. Within small clusters, the configuration of the metal atoms was seen to be constrained to match the surface structure of the γ-Al 2 O 3 , from which likely surface adsorption sites were deduced. A thin, extended raft of rhodium atoms was observed, mostly corresponding to one monolayer. Occasional two-atom features suggested partial dissolution into the top layers of the γ-Al 2 O 3 support.