Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 3: Oberfl
ächenreaktionen I
O 3.6: Vortrag
Freitag, 4. März 2005, 12:00–12:15, TU EB420
Interaction of supported Pd nanoparticles with H, O and C — •Günther Rupprechter, Matthias Morkel, Marta Borasio, and Hans-Joachim Freund — Fritz-Haber-Institut, Faradayweg 4-6, 14195 Berlin
Vibrational sum frequency generation (SFG) spectroscopy, thermal desorption spectroscopy (TDS) and photoelectron spectroscopy (XPS) were utilized to examine the interaction of Al2O3 supported Pd nanoparticles with hydrogen, oxygen and methanol. Experiments were performed both under ultrahigh vacuum (UHV) as well as mbar pressure. The Pd nanoparticles had a mean size of 5 nm and exhibited mostly (111) facets.
Pd-hydride formation was observed to proceed predominantly via minority sites on Pd nanoparticles, i.e. defects and (100) faces. Explosive hydrogen desorption through a CO overlayer originates from the confinement of dissolved hydrogen within the limited nanoparticle volume. The oxidation of Pd nanoparticles under UHV and mbar pressure also seems to be strongly influenced by defects. Carbonaceous deposits that appear during methanol decomposition and oxidation are located both in surface and subsurface positions. A possible involvement of CHx species in the oxidation reaction is discussed.