Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 6: Catalysis
O 6.4: Vortrag
Montag, 16. März 2015, 11:30–11:45, MA 043
Spectromicroscopy of Dynamic Redistribution Patterns of V-Oxide on Rh(111) in Catalytic Methanol Oxidation — •Martin Hesse1, Bernhard von Boehn1, Tevfik Onur Mentes2, Andrea Locatelli2, and Ronald Imbihl1 — 1Institut für Physikalische Chemie und Elektrochemie, 30167 Hannover, Germany — 2Sincrotrone Trieste, 34012 Basovizza, Italy
Upon partial oxidation of methanol to formaldehyde onto a Rh(111) surface with a submonolayer coverage of vanadium one observes a redistribution of the supported vanadium oxide catalyst. Under reaction conditions (10−6 mbar, >560∘C) the initially homogeneous VOx film transforms into a quasi-stationary concentration pattern[1]. Depending on the temperature we find two kinds of patterns, stripes and circular islands. These patterns are investigated with LEEM (low energy electron microscopy), microprobe-LEED (low energy electron diffraction) and microprobe-XPS (X-ray photoelectron spectroscopy). The interior of the VOx islands contains a substructure with an inner boundary separating two regions. Remarkably, the highest V-concentration (θV=0.8MLE) connected with a Moire pattern in LEED is located at the inner boundary whereas left and right of the boundary the V concentration reaches only about half of this value. Transport processes of the reactants that feedback on the V distribution are apparently responsible for this substructure.
[1] F. Lovis and R. Imbihl, J. Phys. Chem. C 115 (2011) 19149-19157