title: On the existence of ordered organic adlayers at the Cu(111)/electrolyte interface.
abstract: We have reinvestigated the behavior of a Cu(111) electrode in pure and cinchonidine containing aqueous 0.1 M HClO4 solution by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (STM). In contrast to previous publications by Wan et al. (Langmuir 2000, 19, 1958-1962 and references cited therein) on Cu(111) in pure 0.1 M HClO4 which claimed an adsorbate-free Cu(111) surface in the entire potential range, we have found a highly ordered hexagonal adsorbate structure with a (4 x 4) unit cell, which is stable in the potential range from hydrogen evolution at -350 to -150 mV (RHE). The adsorbate-free (1 x 1) Cu(111) surface is only visible in a fairly small potential range from -150 to +50 mV. A disordered surface structure is formed at more positive potentials which is interpreted by adsorption of an oxygen-containing species. Furthermore, the formation of a highly ordered cinchonidine adlayer on Cu(111) in 0.1 M HClO4 as reported by Wan et al. (J. Am. Chem. Soc. 2002, 124, 14300-14301) could not be reproduced here. In fact, the similarity of all structures reported by Wan et al. for a great variety of different organic adlayers on Cu(111) in HClO4 solution including cinchonidine with the (4 x 4) superstructure found here already in pure HClO4 solution (i.e., without organic solute) casts serious doubts on the validity of those previous results by Wan et al. in general.
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Wegelerstrasse 12, D-53115 Bonn, Germany. friebel@thch.uni-bonn.de
authors.forename: Daniel
authors.initials: D
authors.lastname: Friebel
authors.forename: Thomas
authors.initials: T
authors.lastname: Mangen
authors.forename: Britta
authors.initials: B
authors.lastname: Obliers
authors.forename: Christian
authors.initials: C
authors.lastname: Schlaup
authors.forename: Peter
authors.initials: P
authors.lastname: Broekmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Wandelt