Methanol Coupling Catalyzed with Gold: Gold surfaces can be effective catalysts for partial oxidation reactions, in part because lower interaction strengths of molecules absorbed on gold allow products to desorb before further unwanted oxidations occur. One challenge in these reactions is the low rate of formation of reactive atomic surface oxygen. Wittstock et al. (p. 319 ; see the Perspective by Christensen and Nørskov ) created high–surface area gold catalysts by leaching silver from gold-silver alloys. This material proved to be an effective catalyst for partial oxidative coupling of methanol, yielding methyl formate. Residual silver appears to play a key role in activating the dissociation of molecular oxygen.

Metal oxide interfaces, metal coatings or dispersed metals on oxide supports play an important part in many technological areas. Nevertheless, there is still a lack of fundamental knowledge about the essential properties of thin metal films and small metal particles on oxide supports, although a deeper understanding could help to improve the electronic, mechanical or catalytic performance of such systems. In the past, a number of different approaches have been proposed and explored aiming at the preparation of suitable model systems. In this review, we discuss the possibility to use thin, well-ordered oxide films as supports for the study of deposited metal particles. This approach offers the advantage to permit the unrestricted application of all experimental methods, which rely on a good electrical or thermal conductivity of the sample, like PES, LEED, STM or TDS. With the help of several examples taken from our own work on a thin alumina film, we show that it is feasible to characterise such systems on a microscopic level with respect to all relevant structural, electronic and adsorption properties. In this way, correlations between these features can be established helping to understand the particular chemistry and physics of small metal aggregates

Nanostructured materials are governed by their surface chemical properties. This is strikingly reflected by np-Au. This material can be generated by corrosion of bulk Ag–Au alloys. Based on a self-organisation process, a 3 dimensional sponge like gold structure evolves with ligaments in the range of only a few tens of nanometers. Due to its continuous porosity, the material can be penetrated by gases which then adsorb and interact with the surface. In this perspective we will review potential applications of np-Au resulting from this effect, namely heterogeneous gas phase catalysis, surface chemistry driven actuation, and adsorbate controlled stability of the nanostructure. We will summarize the current knowledge about the low temperature oxidation of CO as well as the highly selective oxidation of methanol. Furthermore, we will address the question how surface chemistry can influence the material properties itself. In particular, we will deal with (a) the actuation of np-Au by the reversible oxidation of its surface using ozone and (b) the adsorbate controlled coarsening of ligaments, using annealing experiments under ozone or inert gas atmosphere.

Five alumina-supported palladium catalysts have been prepared from a range of precursor compounds [palladium(II) nitrate, palladium(II) chloride, palladium(II) acetylacetonate, and tetraamminepalladium(II) tetraazidopalladate(II)] and at different metal loadings (1–7.3wt%). Collectively, this series of catalysts provides a range of metal particle sizes (1.2–8.5nm) that emphasize different morphological aspects of the palladium crystallites. The infrared spectra of chemisorbed CO applied under pulse-flow conditions reveal distinct groupings between metal crystallites dominated by low index planes and those that feature predominantly corner/edge atoms. Temperature-programmed infrared spectroscopy establishes that the linear CO band can be resolved into contributions from corner atoms and a combination of (111)∕(111) and (111)∕(100) particle edges. Propene hydrogenation has been used as a preliminary assessment of catalytic performance for the 1wt% loaded catalysts, with the relative inactivity of the catalyst prepared from palladium(II) chloride attributed to a diminished hydrogen supply due to decoration of edge sites by chlorine originating from the preparative process. It is anticipated that refinements linking the vibrational spectrum of a probe molecule with surface structure and accessible adsorption sites for such a versatile catalytic substrate provide a platform against which structure/reactivity relationships can be usefully developed.