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Electrochemical Impedance Spectroscopy Investigations of a Microelectrode Behavior in a Thin-Layer Cell:  Experimental and Theoretical Studies

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journal contribution
posted on 19.10.2006, 00:00 by C. Gabrielli, M. Keddam, N. Portail, P. Rousseau, H. Takenouti, V. Vivier
Electrochemical impedance spectroscopy experiments were performed on a microdisk electrode in a thin-layer cell using a scanning electrochemical microscope for controlling the cell geometry. Experimental data showed that when the thin-layer thickness diminished, an additional low-frequency response appeared. It was ascribed to the radial diffusion of the electroactive species and was strongly dependent on the thin-layer dimensions (both thickness and diameter). Moreover, the numerical simulation of the impedance diagrams by finite element method calculations confirmed this behavior. An equivalent circuit based on a Randles-type circuit was proposed. Thus, the diffusion was described by introducing two electrical elements:  one for the spherical diffusion and the other for the radial contribution. A nonlinear Simplex algorithm was used, and this circuit was shown to fit the impedance diagrams with a good accuracy.