title: Dynamics of ultrathin V-oxide layers on Rh(111) in catalytic oxidation of ammonia and CO.
abstract: Catalytic oxidation of ammonia and CO has been studied in the 10(-4) mbar range using a catalyst prepared by depositing ultra-thin vanadium oxide layers on Rh(111) (θV ≈ 0.2 MLE). Using photoemission electron microscopy (PEEM) as a spatially resolving method, we observe that upon heating in an atmosphere of NH3 and O2 the spatial homogeneity of the VOx layer is removed at 800 K and a pattern consisting of macroscopic stripes develops; at elevated temperatures this pattern transforms into a pattern of circular VOx islands. Under reaction conditions the neighboring VOx islands become attracted by each other and coalesce. Similar processes of pattern formation and island coalescence are observed in catalytic CO oxidation. Reoxidation of the reduced VOx catalyst proceeds via surface diffusion of oxygen adsorbed onto Rh(111). A pattern consisting of macroscopic circular VOx islands can also be obtained by heating a Rh(111)/VOx catalyst in pure O2.
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Leibniz Universität Hannover, Callinstrasse 3-3a, D-30167 Hannover, Germany. imbihl@pci.uni-hannover.de.
authors.forename: B
authors.initials: B
authors.lastname: von Boehn
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Leibniz Universität Hannover, Callinstrasse 3-3a, D-30167 Hannover, Germany. imbihl@pci.uni-hannover.de.
authors.forename: A
authors.initials: A
authors.lastname: Preiss
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Leibniz Universität Hannover, Callinstrasse 3-3a, D-30167 Hannover, Germany. imbihl@pci.uni-hannover.de.
authors.forename: R
authors.initials: R
authors.lastname: Imbihl