Metal oxide catalysts are more complex than conventional metal catalysts because they can terminate with different functionalities and expose cations in multiple oxidation states.  The combination of two metals in an oxide matrix can produce materials with novel structural or electronic properties that can lead to distinct catalytic activity or selectivity.  To rationalize structure-reactivity relationships for mixed-metal oxide catalysts at the atomic level, well-defined systems are required.  Our recent studies involving the deposition of nanoparticles and clusters of RuOx or CeOx on TiO2(110) have shown novel structures that have special chemical properties.  After deposition on TiO2(110), we have found the formation of ceria dimers and 1D structures of RuOx.  The non-typical coordination modes imposed by TiO2(110) on ceria nanoparticles make possible the direct participation of this oxide in catalytic reactions and enhance the dispersion of metals on the titania substrate.  M/CeOx/TiO2(110) (M = Au, Cu, Pt) surfaces display an extremely high catalytic activity for CO oxidation and the water-gas shift reaction.  The 1D structures for RuO2 deposited on TiO2(110) can be easily reduced and re-oxidized, displaying a very high catalytic activity for CO oxidation.  In general, the chemical behavior of the MOx/TiO2(110) {M = V, W, Ce or Ru} surfaces reflects their unique structure at the nanometer level.  These simple models can provide a conceptual framework for modifying or controlling the chemical properties of mixed-metal oxides and for guiding the engineering of novel industrial catalysts.Supported by the US Department of Energy, Office of Basic Energy Sciences (DE-AC02-98-CH10086)

Catalysis and the nature of mixed-metal oxides at the nanometer level

243rd National Meeting (2012)

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