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O: Fachverband Oberflächenphysik

O 60: Poster Session IV (Solid/liquid interfaces; Semiconductors; Oxides and insulators; Graphene; Plasmonics and nanooptics; Electronic Structure; Surface chemical reactions; Heterogeneous catalysis)

O 60.111: Poster

Wednesday, March 16, 2011, 17:30–21:00, P4

Selforganization in ultrathin, K-promoted V-oxide layers on Rh(111) during the O2+H2 reaction. — •Martin Hesse, Fernando Sotoca Usina, and Ronald Imbihl — Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover, Callinstr. 3 - 3a, D-30167 Hannover, Germany

Alkali metals (AM's) promoted V-oxides play an important role as catalysts in a number of industrial partial oxidation reactions. As catalytic model system we studied the behaviour of K-promoted ultrathin V-oxide films (0.25 ML of V) on Rh(111) in the O2+H2 reaction using photoemission electron microscopy (PEEM) as spatially resolving method. With LEED, ordered phases of the ternary system V+K-O were detected. Similar to the unpromoted system stationary patterns develop under reaction conditions formed by stripes of V+O+K surrounded by bare Rh(111) surface. In addition, we observe also dynamic chemical wave patterns leading to K redistribution and enrichment of K at interfaces. The main effect of the addition of the AM is that it makes the VOx system very dynamic as evidenced by violent chemical turbulence. Tentatively, the stationary patterns were explained as being a consequence of reactive phase separation.