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O: Fachverband Oberflächenphysik

O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)

O 42.65: Poster

Mittwoch, 25. März 2009, 17:45–20:30, P2

In situ STM study of Cu modified Au(1 0 0) electrodes in alkaline solution — •Christian Schlaup and Klaus Wandelt — Institute for Physical und Theoretical Chemistry, University of Bonn, Wegelerstr. 12, D-53115 Bonn

Ultrathin Cu layers were prepared on Au(1 0 0) electrodes using the well-known Cu underpotential deposition. After a two step electrolyte exchange process these Cu modified Au(1 0 0) electrodes were exposed to a 0.01 M NaOH electrolyte. In dependence on the electrochemical potential different surface structures were found and characterized. Starting at low potentials where the adsorbate free pseudomorphic Cu adlayer remains stable, two barely ordered structures were formed during potential increase. In a first step OH⁻ ions are adsorbed, forming an largely disordered overlayer with a next neighbor distance of about 0.6 nm. During further potential increase the Cu layer is oxidized yielding a CuO film, which shows a characteristic stripe structure. In contrast to bulk Cu(1 0 0) electrodes, where a two step oxidation process via an intermediate Cu₂O species was found, the CuO film is formed directly under these conditions. However, an additional structure was found in the transition regime between the uncovered and OH⁻ covered Cu layer. After keeping the potential constant for at least 20 minutes, islands with a hexagonal lattice and a next neighbor distance of about 0.3 nm appear. Both, the small lattice constant and the slow kinetic may point to the formation of a Au/Cu surface alloy.