Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 3: Oberfl
ächenreaktionen I

O 3.8: Vortrag

Freitag, 4. März 2005, 12:30–12:45, TU EB420

In-situ high resolution XPS study of the CO oxidation on Pt(355) — •Barbara Tränkenschuh, Thomas Fuhrmann, Christian Papp, Daniel Kiessling, Reinhard Denecke, and Hans-Peter Steinrück — Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen

The oxidation of CO on the stepped Pt(355)=[5(111)x(111)] surface was studied by in-situ high resolution XPS experiments at BESSY II. The different species and adsorption sites (O, CO on-top/bridge) on steps and terraces are clearly distinguishable in O 1s or C 1s spectra. In the experiments first an oxygen layer was prepared using a procedure, which leads to a p(2x2)-O-LEED pattern on Pt(111). On Pt(355), however, no ordered adsorbate structure was observed. Therefore, the coverages of the reactants (O, CO) were estimated by comparing the XPS intensities with those observed on Pt(111) [1]. CO was dosed by a supersonic molecular beam, which allows to vary the CO pressure on the sample. The oxidation was studied as a function of reaction temperature and CO pressure on the sample by recording time-dependent O 1s and C 1s intensities. Measurable reaction rates on Pt(355) are observed at much lower temperatures than on Pt(111) (200 vs. 270 K, respectively) [1]. The reaction product CO₂ was additionally detected by mass spectrometry. Supported by the DFG (STE 620/4-2).

[1] M. Kinne et al., J.Chem. Phys. 120 (2004) 7113.