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Christmann K.,Institute For Chemie Und Biochemie Der Fu Berlin | Schwede S.,Institute For Chemie Und Biochemie Der Fu Berlin | Schubert S.,Institute For Chemie Und Biochemie Der Fu Berlin | Kudernatsch W.,University of Aarhus
ChemPhysChem | Year: 2010

The peculiar catalytic activity of Au-supported titanium dioxide surfaces in the CO oxidation reaction has been a focus of interest for more than twenty years. Herein, recent data concerning preparation and structural characterisation of planar catalyst model systems consisting of single-crystalline titania and/or gold nanoparticles deposited thereon is presented and reviewed. We first expand on the deposition and growth of TiO2 films on selected metal host surfaces and then consider the deposition of Au nanoparticles on these surfaces, including in-formation on their geometric and electronic structures. The second issue is the interaction of these materials with carbon monoxide (one of the essential ingredients of the CO oxidation reaction) which serves as a probe molecule and monitor of the chemical activity of the model catalyst samples. Concerted efforts relating the structural and chemical properties of the respective binary materials (titania support plus deposited gold) can help to tackle and finally resolve the still open problems concerning the high activity of Au-TiO2 catalysts in the CO oxidation reaction. © 2010 Wiley-VCH Verlag GmbH & Co.


Przyrembel D.,Institute For Chemie Und Biochemie Der Fu Berlin | Przyrembel D.,Institute For Experimentalphysik Der Fu Berlin | Messahel L.,Institute For Chemie Und Biochemie Der Fu Berlin | Christmann K.,Institute For Chemie Und Biochemie Der Fu Berlin
Journal of Physics Condensed Matter | Year: 2013

We have studied the adsorption of copper on the clean Re.10N10/ surface between 300 and 900 K by means of low- and medium-energy electron diffraction (LEED and MEED) and temperature-programmed thermal desorption (TPD). The persistence of a .1 1/ LEED pattern during Cu deposition suggests the formation of pseudomorphic Cu islands. Accordingly, the intensityvoltage behaviour of the .1 1/ LEED beams can be quantitatively superimposed by the coverage-weighed fractions of the I.V/-curves of uncovered Re areas and of Cu-covered .1 1/ islands. At a coverage of 1:625 1019 Cu atoms m2 dynamical LEED I.V/ calculations suggest a full hcp-oriented Cu bilayer (BL). Within this first BL, Cu wets the Re surface completely, while all following layers exhibit remnant roughness due to small Cu nuclei, as confirmed by in situ grazing-incidence MEED experiments. The completion of the first BL coincides with the saturation of a single TPD state at 1180 K, whilst higher coverages produce an additional zero-orderst state which peaks at 1080 K at 2.6 BL. The energy of desorption rises from 320 kJ mol 1 at small coverages to360 kJ mol 1 for a bilayer Cu film, pointing to attractive lateral CuCu interactions. An analysis of the leading edge of the multilayer state yields a desorption energy of 305 kJ mol 1, somewhat lower than the sublimation enthalpy of bulk Cu. Our data are discussed and compared with previous results on related systems. © 2013 IOP Publishing Ltd.


PubMed | Institute For Chemie Und Biochemie Der Fu Berlin
Type: Journal Article | Journal: Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2011

We have deposited Au films in ultra-high vacuum onto a rhenium ([Formula: see text]) surface in submonolayer and multilayer concentrations and studied them by means of low-and medium-energy electron diffraction in the temperature range between 300 and 800K. In the submonolayer range, Au forms several low-energy electron diffraction (LEED) phases, namely, a (1 3), a (1 4), a (1 5) and a (1 6) phase, consisting of one-dimensionally ordered Au chains in the [[Formula: see text]] direction, until the formation of a complete pseudomorphic monolayer is indicated by a (1 1) LEED phase. In the multilayer regime, a (1 8) LEED phase appears over a surprisingly wide coverage range from about two to at least eight monolayers, which we interpret as a hexagonal uniaxially compressed reconstructed Au overlayer on pseudomorphically grown hexagonal close-packed gold layers. In order to get access to absolute Au coverages, we have performed LEED (I,V) measurements and carried out a LEED structure determination for the (1 1) phase. We propose the formation of a full Au monolayer in which both the Re trough and top-row sites are being covered by Au atoms. The data are discussed and compared with those from previous studies on related systems.


PubMed | Institute For Chemie Und Biochemie Der Fu Berlin
Type: Journal Article | Journal: Chemphyschem : a European journal of chemical physics and physical chemistry | Year: 2010

The peculiar catalytic activity of Au-supported titanium dioxide surfaces in the CO oxidation reaction has been a focus of interest for more than twenty years. Herein, recent data concerning preparation and structural characterisation of planar catalyst model systems consisting of single-crystalline titania and/or gold nanoparticles deposited thereon is presented and reviewed. We first expand on the deposition and growth of TiO(2) films on selected metal host surfaces and then consider the deposition of Au nanoparticles on these surfaces, including information on their geometric and electronic structures. The second issue is the interaction of these materials with carbon monoxide (one of the essential ingredients of the CO oxidation reaction) which serves as a probe molecule and monitor of the chemical activity of the model catalyst samples. Concerted efforts relating the structural and chemical properties of the respective binary materials (titania support plus deposited gold) can help to tackle and finally resolve the still open problems concerning the high activity of Au-TiO(2) catalysts in the CO oxidation reaction.

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