Dynamic electrochemical impedance spectroscopy for the charge transfer rate measurement of the ferro/ferricyanide redox couple on gold
Tamás Pajkossy, Maximilian U. Ceblin, Gábor Mészáros
Abstract
The use of dynamic electrochemical impedance spectroscopy, dEIS is shown in the context of diffusion-controlled electrode reactions. By this method, a number of audio-frequency impedance spectra were measured on a gold electrode in an aqueous solution of K4[Fe(CN)6] while taking cyclic voltammograms (the CVs were taken with 50–200 mV/s scan-rate; the distance of potentials of impedance spectra was 16 mV). The Faradaic impedance elements were determined from the spectra, from them charge transfer rate coefficients were calculated; it was found to be 0.11 cm/s at the formal potential. This set of measurements demonstrates the main advantage of dEIS over the traditional steady state impedance measurements: dEIS characterization of an electrochemical system can be performed in seconds rather than minutes which makes possible to use freshly prepared (e.g., annealed) electrodes with reduced risk of contamination or modification of their surfaces.