Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 9: Adsorption an Oberfl
ächen I
O 9.9: Vortrag
Montag, 24. März 2003, 17:00–17:15, FOE/ANOR
Dissociative adsorption of methane on Ni(111) observed by high resolution XPS — •Thomas Fuhrmann, Martin Kinne, Junfa Zhu, Barbara Tränkenschuh, Reinhard Denecke, and Hans-Peter Steinrück — Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen
Alkanes show in general a strong dependence of their dissociative sticking probability on metal surfaces on the kinetic energy of the impinging molecules. Due to the application of Ni as a catalyst for steam reforming, a study of the adsorption of methane on nickel surfaces may allow deeper insights to reaction mechanism. For this reason, we have explored the chemical nature of the adsorbed species on Ni(111) in dependence of the kinetic energy and also of the excitation of vibrational states of methane. Using a supersonic beam to control the energy of the molecules in combination with high resolution XPS at the synchrotron facility BESSY II enables us to perform these experiments. In dependence of the different energies of the impinging molecules, only one species is populated at a surface temperature of 110 K. It is assigned to CH3 from analysis of the C 1s core level spectra. From time-dependent measurements the adsorption kinetics are determined. Using temperature-programmed photoelectron spectroscopy (TPXPS) we are also able to observe the thermal evolution of the adsorbed CH3. Various intermediate species on the surface are observed until finally pure carbon is formed by dehydrogenation. The results will be discussed in comparison to the system CH3 on Pt(111) and by using spectra obtained for possible intermediate species. Supported by the DFG (STE 620/4-1).