Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 26: Adsorption an Oberflächen II

O 26.4: Vortrag

Dienstag, 9. März 2004, 16:30–16:45, H45

CO-H interaction and H-dissolution probed by SFG and TDS: Specific differences between Pd nanoparticles and Pd(111) — •Günther Rupprechter, Matthias Morkel, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

CO hydrogenation and H bulk dissolution on Pd model catalysts were studied by sum frequency generation (SFG) vibrational spectroscopy and thermal desorption spectroscopy (TDS) at pressures ranging from ultrahigh vacuum (UHV) to 1 bar. Well-facetted Pd nanoparticles (ca. 5 nm), grown on Al2O3/NiAl(110), as well as Pd(111) were employed as model surfaces and examined using a UHV-compatible high-pressure cell. Although the Pd nanoparticles mostly exhibt (111) faces, their adsorption/reaction behaviour is quite different from Pd(111).

Strong differences with respect to the adsorption of the individual molecules were observed, e.g. an easier formation of a hydride phase on Pd nanoparticles. Even more pronounced differences occurred for CO-H coadsorbate structures under UHV and mbar pressure which are strongly related to the formation of bulk H. It is demonstrated that the dynamic adsorbate structure of a high-pressure reaction can not be mimicked under the static conditions of a UHV experiment.

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