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 VO_x 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 VO_x islands contains a substructure with an inner boundary separating two regions. Remarkably, the highest V-concentration (θ_V=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