Adsorption of Perchlorate Ions on Au(111) Electrodes
U.E. Zhumaev, A. Kuzume, I.V. Pobelov, A.V. Rudnev, Th. Wandlowski
Department of Chemistry and Biochemistry, University of Bern
Freiestrasse 3, 3012 Bern, Switzerland
[email protected]
Adsorption and desorption of anions are involved in various important
electrochemical processes on noble metal electrodes, such as hydrogen adsorption,
surface reconstruction, underpotential deposition, surface oxidation, and oxygen
evolution [1]. There are only a few of the anions which are considered as adsorbing
almost physically. On gold surfaces
ClO4- is weakly adsorbed [2],
suggesting incomplete charge transfer
from ClO4- to gold. Nevertheless, it
was argued that ClO4- ions adsorb on
Au(111) with complete charge
transfer [2].
ClO4- adsorption and desorption
are fast processes on polycrystalline
Au electrodes, and are characterized
by symmetric (with respect to j = 0)
cyclic voltammograms at low scan
rates. The latter is not the case for
Fig. 1: Lines: cyclic voltammograms (scale on
Au(111) electrodes in ClO4- solutions
the left) of the Au(111) electrode in 0.1 M
-1
even at the rate of 10 mV s (Fig. 1,
HClO4: first (dashed) and second (dotted) cycles
dotted). The reason for the
of thermally-reconstructed surface (10 mV s-1)
asymmetry could be a change in
and response of the unreconstructed surface
surface structure of a Au(111)
(solid) recorded starting from 0.3 V (18 V s-1).
electrode (surface reconstruction),
Symbols: normalized integrated intensities of νClO
(scale on the right) obtained by SEIRAS during
and/or rearrangement within the
potential scan at 10 mV s-1. The reference
adsorbed ClO4- layer, and/or other
spectrum was acquired at - 0.65 V.
intrinsic property of a Au(111)
surface.
In this study, we report ClO4- adsorption geometry and properties on Au(111)
electrodes. Our experimental strategy is based on the combination of electrochemical
measurements and in situ IR and Raman spectroscopy techniques to characterize the
structure of the Au(111)/ClO4- interface during the adsorption process (Fig. 1,
symbols). We show that only the surface reconstruction causes the abovementioned
asymmetry and that the reconstruction process can be eliminated at high scan rates
(Fig. 1, solid). Based on cyclic voltammograms we provide a relation between
potentials of zero charge for reconstructed and unreconstructed Au(111) surfaces.
References
[1] A. Wieckowski, Interfacial Electrochemistry. Theory, Experiment, and
Applications, in, Marcel Dekker, Inc., New York, 1999.
[2] B.E. Conway, Progress in Surface Science 49 (1995) 331.
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