In order to explore possible origins of the frequency dispersion of the interfacial capacitance observed for single crystal electrodes. voltammetric and impedance experiments on Au(hkl) 1 aqueous electrolyte interfaces were combined with structural studies employing in situ scanning tunnelling microscopy and surface X-ray diffraction. The observed capacitance dispersion on Au(hkl)-surfaces in the absence of strongly specifically adsorbed ions is mainly attributed to the restructuring of the substrate surface. Dominant contributions due to a slow diffusion and/or adsorption step were found in a case study with specifically adsorbed bromide ions on Au(lOO). Attempts to generalize the observations with simple ions towards the more complex adsorption and phase formation of organic molecules on single crystal gold electrodes did not provide a one-to-one correlation between the structural data and capacitance or impedance studies. The test example chosen, 2,2'-BP/Au(111), demonstrates i) the complexity of inter- facial processes which may take place even for seemingly simple systems and ii) illustrates convincingly some of the critical limits of classical electrochemical techniques.
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