Abstract

HAMMADI, A.  and  BERD, M.. Capacitive Dispersion of Ag-15%Cu/0.1 M HClO₄ Interface: Pre-treatment and Adsorption Effects. Port. Electrochim. Acta [online]. 2005, vol.23, n.4, pp.437-444. ISSN 0872-1904.

The interfacial impedance (or shortly, the capacitance) of solid electrodes in the absence of faradaic reactions usually deviates from purely capacitive behaviour. On polycrystalline solid electrodes "frequency dispersion capacitance" is often observed. We present qualitative impedance experiments on pre-treated Ag-15%Cu alloy electrodes immersed in 0.1 M HClO₄. The results suggest that models taking into account microscopic geometrical aspects only (i.e. roughness) are not suitable for interpreting the de facto link between roughness and capacitance dispersion. Instead, considering additional points, such as surface heterogeneities on an atomic scale (i.e. surface disorder) together with adsorption of certain ionic species, particularly the Cl^-, on the surface of the metal can and do cause capacitance dispersion in the frequency range relevant in electrochemistry.

Keywords : solid polycrystalline electrodes; capacitance dispersion; electrochemical impedance spectroscopy; heterogeneity; atomic scale; roughness; adsorption; constant phase angle element (CPE).

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