Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)

O 59.66: Poster

Wednesday, March 24, 2010, 17:45–20:30, Poster B1

Competitive Adsorption of Viologen Species on a Chloride Modified Copper (100) Surface — •Martino Saracino¹, Nguyen Thi Minh Hai², Peter Broekmann², and Klaus Wandelt¹ — ¹Institut of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany — ²Interfacial Electrochemistry Group, Department of Chemistry and Biochemistry, University of Berne, Freiestr. 3, 3012 Berne, Switzerland

A number of technological relevant processes involve charge transfer reactions at electrified solid\liquid-interfaces. Their microscopic understanding requires the study of the electrode surface under in situ reactive conditions, for instance STM and cyclic voltammetry. The competitive adsorption of Diphenyl- (DPV) and Dibenzylviologen (DBV) on a Cl⁻ modified Cu(100) surface was chosen as model system for similar N-containing aromatic molecules, which play a significant role as additives in metal plating. Upon adsorption DPV²⁺ is reduced even at most anodic potentials to the monocationic radical DPV^+* and forms a full monolayer of a hydrophobic π-stacked stripe phase which, however, does not prevent further redox reactions to take place. Lowering the electrode potential to the DBV²⁺ reduction potential at -250mV [RHE] leads to the replacement of the DPV^+* phase by a π-stacked stripe phase consisting of the produced monocationic DBV^+*. Conversely, returning to the DPV^+* oxidation potential at -100mV [RHE] leads to a re-substitution of the DBV^+*- by the initial DPV^+*-stripe phase. In contrast to mono-viologen systems no stable dicationic phases have been observed at all.