Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 9: Adsorption an Oberfl
ächen I
O 9.5: Vortrag
Montag, 24. März 2003, 16:00–16:15, FOE/ANOR
Adsorption Properties of Hydrogen on Rhodium - Vanadium alloy surfaces — •Robert Schennach, Georg Krenn, and Klaus D. Rendulic — Institute of Solid State Physics, Graz University of Technology, Austria
Within a larger effort to study the interactions of V modified Pd and Rh surfaces with simple gases, the system Rh (111) and V was studied in detail. The influence of two types of stable V modified Rh (111) surfaces (V islands (1/3 monolayer V) on top of the Rh surface and a subsurface alloy with 1/4 monolayer of V in the second atomic layer) on the adsorption and desorption behavior of hydrogen is presented. Adsorption of hydrogen on Rh (111) has been shown earlier to proceed via dynamical steering. The sticking coefficient as a function of translational energy of H2 and D2 points to adsorption via dynamical steering on both V modified surfaces. The adsorption is influenced by the downshift of the metal d-band due to alloying with V. Thermal desorption spectra from the surface with V islands and from the Rh (111) surface are similar. On the subsurface alloy an additional peak at lower temperatures is found during thermal desorption. The origin of this peak can be explained in terms of a reconstruction of the alloy during adsorption and desorption and/or additional hydrogen adsorption in subsurface sites. The maximum coverage of hydrogen on all three surfaces was determined quantitatively.