Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 62: Metal Substrates: Adsorption of Inorganic Molecules

O 62.11: Talk

Thursday, February 28, 2008, 12:00–12:15, MA 042

CO adsorption on Ag/Pd(111) surface alloy — •Yunsheng Ma, Joachim Bansmann, and Rolf Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm

The growth of Ag on Pd(111), Ag/Pd surface alloy formation and the chemical properties of these surfaces using CO probe molecules were studied by X-ray Photoemission Spectroscopy (XPS), CO Temperature Programmed Desorption (TPD) and High Resolution Electron Energy Loss Spectroscopy (HREELS). At room temperature, thermal evaporation of Ag leads to a layer-by-layer growth mode on Pd(111) [1]. Annealing the Ag film induces a down-shift of the binding energy of the Ag 3d peak by 0.6 eV, indicating surface alloy formation. CO desorption peaks in the temperature range between 350 K and 500 K are observed upon varying the Ag/Pd ratio of the surface alloy. The different CO TPD peaks obtained on Ag/Pd surface alloys can be attributed to CO desorption from different Pd/Ag or Pd ensemble. The results are discussed in comparison with previous experimental and theoretical results on Au/Pd(111) [2].

[1] B. Eisenhut, J. Stober, G. Rangelov, Th. Fauster, Phys. Rev. B 47 (1993) 12980

[2] M. Ruff, N. Tahehiro, P. Liu, J.K. Norskov, R.J. Behm, Chem. Phys. Chem. 8 (2207) 2068