Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 3: Adsorption I
O 3.3: Vortrag
Montag, 27. März 2006, 11:45–12:00, TRE Phys
The influence of steps on the activated adsorption of methane on platinum: a molecular beam / high-resolution XPS study. — •Christian Papp, Barbara Tränkenschuh, Regine Streber, Thomas Fuhrmann, Reinhard Denecke, and Hans-Peter Steinrück — Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen.
We investigated the activated adsorption of methane on Pt(644) and Pt(355) to examine the influence of steps on the sticking coefficient and, thus, on the reactivity of these surfaces. Both samples have (111) terraces and differ only in the step orientation: Pt(644) has (100) steps and Pt(355) has (111) steps. To overcome the barrier for methane dissociation at UHV conditions, we used a supersonic molecular beam set-up. From measurements on Pt(111)[1], methyl (CH3) has been identified as the product of the dissociative adsorption. By using high resolution in-situ XP spectroscopy we are able to distinguish between methyl adsorbed at step and terrace sites. The adsorption processes were analysed separately, leading to relative sticking coefficients for step and terrace adsorbed molecules, with a different kinetic energy dependence. Additionally, we investigated the thermal evolution of the adsorbed species to study the influence of the steps on the dehydrogenation process. A comparison to corresponding results for flat Pt(111)[2] will be presented. Supported by the DFG (STE 620/4-3).
[1] Fuhrmann et al., Chem. Phys. Lett. 390 (2004) 208.
[2] Fuhrmann et al., New J. Phys. 7 (2005) 107.