1708
Artefacts in Electrochemical Impedance Measurements Due to Stray Capacitances
Even in the case of ideal reference electrode positioning and a very high analyzer input impedance, stray capacitances between the three electrodes can lead to impedance artefacts. Stray capacitances can be minimized, but they cannot be eliminated completely. By means of a three-terminal equivalent network, Fletcher showed that stray capacitances can cause artefacts over the entire frequency range. However, Fletcher considered the electrodes to be purely resistive.[3] Sadkowski et al. extended this model and considered the working electrode to have a complex impedance consisting of a parallel RC-circuit in series with a resistor, representing the charge transfer resistance, the double-layer capacitance and the electrolyte resistance, respectively. However, the counter electrode and the reference electrode are still considered to be purely resistive.[4]
In this work we present results for an extended model in which all three electrodes exhibit a complex impedance consisting of a parallel RC element in series with a resistor (see figure 1). Using this model, it is e.g. possible to calculate the three-electrode impedance spectra of an electrochemical cell with blocking and non-blocking electrodes. By comparing model spectra with experimental spectra, the stray capacitances in electrochemical cells can be estimated.
Figure 1: Three-terminal equivalent network used for the simulations.
[1] G. Hsieh, S. J. Ford, T. O. Mason, L. R. Pederson, Solid State Ionics, 91, 191 (1996).
[2] S. Klink, E. Madej, E. Ventosa, A. Lindner, W. Schuhmann, F. La Mantia, Elechtrochemistry Communications, 22, 120 (2012).
[3] S. Fletcher, Elechtrochemistry Communications, 3, 692 (2001).
[4] A. Sadkowski, J.-P. Diard, Electrochimica Acta, 55, 1907 (2010).