Current commercial heterogeneous catalysts are structurally and chemically complex and data gathered from them can seldom be interpreted with atomic-level precision. The focus of this symposium was to reduce the complexity of oxide based catalysts to the levels addressable and controllable at the atomic scale while maintaining intimate linkages with practical catalysis and catalytic materials. Current experimental and theoretical advances present us with the opportunity to describe and control metal oxide catalytic systems at an atomic level. Presentations leading to the understanding of fundamental principles and structure-reactivity relationships formed the focal point of this symposium. The crucial synergistic approach between theory and experiment was readily apparent in the talks. Sessions dealt with model metal and metal-oxide catalytic systems, nanoscale induced reactivity, structure-reactivity relationships, and non-thermal processes. These topics stimulated a vigorous exchange of ideas and the formation of new collaborations in this interdisciplinary field. The symposium was well attended with an average of 50 attendees per session.

The international speakers supported by PRF included leading experts from around the world. Their talks expanded the scope of this symposium immensely and contributed to the excellent attendance at this event. Their contributions are briefly summarized below:

Flemming Besenbacher: Scanning Tunneling Microscopy Studies of Reactions on TiO₂(110)

Transition-metal oxide surfaces play an important role in a wide range of applications. Defects like oxygen vacancies often dominate electronic and chemical properties of transition-metal oxide surfaces. Our recent studies on a rutile TiO₂(110) surface exploited the high-resolution, variable-temperature and fast-scanning STM to study how oxygen vacancies influence surface and interface reactions.

Maciej Gutowski: Theoretical studies of planar model transition metal oxide catalysts

The structures of WO₃(001) and ReO₃(001) were simulated using density functional theory. The calculations showed that the interactions of methanol are stronger on ReO₃(001) (-103 kJ/mol) than on WO₃(001) (-74 kJ/mol). The dissociation of methanol to form adsorbed methoxy and H adatom is highly endothermic on WO₃(001) with a heat of reaction of 108 kJ/mol. The same reaction on ReO₃(001) is exothermic by -9 kJ/mol. An activation barrier for methanol dissociation over ReO₃(001) is ~18 kJ/mol.

Ulrich Heiz: Deposition of Mass-selected Metal Clusters on Oxide Surfaces

The exceptional catalytic properties of small gold aggregates have motivated research aimed at providing insights into the molecular origins of this unexpected reactivity of gold. Investigations on size-selected small gold clusters, Au_n (n = 2 - 20), softlanded on a well-characterized MgO(001) surface with and without oxygen vacancies or F centers, revealed that gold octamers bound to F centers of the magnesia surface are the smallest known gold heterogeneous catalysts that can oxidize CO into CO₂ at temperatures as low as 140 K.

Hiroshi Onishi: Imaging of Surface Photochemical Reactions

Results presented in this talk on a model TiO₂ photocatalyst, rutile TiO₂(110), provide more detailed information on the roles of O₂ and show that O₂ not only acts as an electron scavenger but also is involved in thermal reactions with organics and OH groups. Results on the photo-oxidation of trimethyl acetate, isobutene and acetone were used to illustrate these functions of O₂ during photocatalysis on TiO₂.

Gianfranco Pacchioni: Metal Atoms and Clusters on Oxide Surfaces and Thin Films

Recent studies have shown that supported charged metal clusters, and in particular cluster anions, are catalytically more active than their neutral counterparts. Charging mechanisms of metal atoms and clusters on oxide surfaces was the topic of this talk.

Geoff Thornton: Alkali Modified Oxide Surfaces

Alkali and alkaline earth metals are known to behave as reaction modifiers on a variety of substrates, including metal oxides. Understanding their role in terms of structure, both physical and electronic, is a key challenge, with practical applications in areas such as gas sensors and microelectronics. The deposition and segregation of alkali and alkaline earth metals on titanium dioxide was a particular focus of this talk.