ABSTRACT
The structure and the composition of the electrode/electrolyte interface is of great scientific and technological interest. It is generally accepted that the adsorption of anions and cations from the solution is the initial step for many important electrochemical processes such as oxide formation, pitting corrosion, electrocatalysis and metal or semiconductor deposition. Classical electrochemical techniques, which are in principle based on potential and current measurements, are able to reveal a detailed description of the electrochemical interface. For example, the kinetics of oxide or chloride film formation on several different metals have been investigated with a high accuracy, and different growth modes can easily be identified [1-3]. In some cases, also a microscopically detailed picture of the electrode surface can be derived. For example, each single crystal metal surface in a well defined electrolyte shows a typical cyclic voltammogram which can be used for a simple control of the single crystal surface preparation (as an example see [4-6]); in contrast to the large experimental expenditures which are necessary for a conventional surface structure analysis e.g. with low energy electron diffraction (LEED) or grazing incidence x-ray diffraction. For the underpotential deposition (upd) of copper on stepped platinum surfaces, a clear influence of the copper coverage on the hydrogen adsorption reaction was found; even small amounts of adsorbed Cu on the Pt surface are able to block the hydrogen adsorption reaction [7, 8]. Due to the fact that this reaction preferentially takes place at Pt step sites, one can directly deduce that the blocking of hydrogen adsorption is a consequence of the selective adsorption of Cu at step sites [8].
