Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 40: Oxides and insulators
O 40.6: Vortrag
Donnerstag, 30. März 2006, 16:15–16:30, WIL A317
Composition, structure, and catalytic activity of sulfated c-ZrO2(111) films on Pt(111) — •Stefan Förster1, Klaus Meinel1, Alexander Hofmann2, Ralf Kulla1, Karl-Michael Schindler1, Henning Neddermeyer1, Joachim Sauer2, and Wolf Widdra1 — 1Martin-Luther-Universität Halle-Wittenberg, FB Physik, D-06099 Halle, Germany — 2Humboldt-Universität zu Berlin, Institut für Chemie, D-10099 Berlin, Germany
Sulfated zirconia catalysts are very active in the low-temperature isomerization of n-alkanes. Single crystalline sulphated c-ZrO2(111) films of the cubic (c) type have been prepared as a model catalyst by reactive deposition of Zr onto Pt(111) in an O2 atmosphere and subsequent exposition to a SO3 atmosphere. Structure and composition of the film surface have been examined by scanning tunneling microscopy, low-energy electron diffraction (LEED), Auger electron spectroscopy, and density functional theory (DFT) calculations. The clean c-ZrO2(111) films display a (2x2) surface structure. During SO3 exposure, a clear (√3x√3)R30∘ structure develops. At about 700 K, the (√3x√3)R30∘ structure disappears and the bright LEED pattern of the clean ZrO2 films reappears. The energies of plausible c-ZrO2(111)/SO3 structures have been examined by DFT. The (√3x√3)R30∘ structure found in the experiments turned out to be the most stable one for temperatures below 700 K. During reaction with n-butane, the (√3x√3)R30∘ sulfation structure is stable and its chemical activity is indicated by the formation of surface carbon.