AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP5
Ordered Structures of Oxo Overlayer on Cu(111) Electrode Surface in an Alkaline Electrolyte Revealed by Electrochemical STM

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: O. Matsuoka, Mitsui Chemicals, Inc., Japan
Authors: O. Matsuoka, Mitsui Chemicals, Inc., Japan
S. Yamamoto, Mitsui Chemicals, Inc., Japan
S. Sugiyama, Mitsui Chemicals, Inc., Japan
H. Nozoye, National Institute of Materials and Chemical Research, Japan
Correspondent: Click to Email
Redox behavior of copper surface in aqueous solution is of great interest in many industrial fields, such as energy, catalytic, and microelectronic applications. Many characterization studies on copper electrode surface revealed that surface oxygen is not entirely removed even at the potential corresponding to the onset of hydrogen evolution. This oxo overlayer on surface is considered active for catalytic reactions.@footnote 1@ Information about the structure and behavior of oxo overlayer in aqueous solutions seems to provide a proper understanding of reacting mechanism of copper catalysts. We have investigated the structure of Cu(111) electrode surface that have an oxo overlayer in an 0.01M NaOH aqueous solution by using electrochemical scanning tunneling microscope (EC-STM). Two kinds of periodical structures of bright spots were observed.@footnote 2@ Dimensions of these periodical structures were similar to the unit cell for the (@sr@7 x @sr@7) and (2@sr@7 x 2@sr@7). The periodical structure similar to (@sr@7 x @sr@7) appeared at a cathodic wave at -0.9 V vs. Ag/AgCl on cyclic voltammogram, and this periodical structure was converted into (2@sr@7 x 2@sr@7) at more negative potential. Anodic wave related with the cathodic wave at -0.9 V appeared in anodic sweep. The potential of this anodic wave was different between these two periodical structures. We consider these periodical structures show an alignment of CuOH surface species which created by the reduction of sub-surface oxygen.@footnote 3@ @FootnoteText@ @footnote 1@L.D.Burk, et al., J.Electrochem.Soc., 137,553(1990) @footnote 2@O.Matsuoka, et al., Chem.Lett., 947(1998) @footnote 3@S.Haetinger, et al., J.Electroanal.Chem., 397,335(1995).