Analysis of high-frequency distortions in impedance spectra of conducting polyaniline film modified Pt-electrode measured with different cell configurations

Distortions of high-frequency parts of impedance spectra of conducting polyaniline, PANI, film modified Pt electrodes in 0.5 and 0.05 mol dm−3 H2SO4 are analysed in terms of overlapping between impedance of PANI film working electrode (WE) branch and artefact impedance(s) induced by measurements in two-electrode (symmetrical, PANI versus PANI and asymmetrical, PANI versus platinised Pt) and three-electrode (with conventional reference (RE) and pseudo-reference (PRE) electrode) cells. In impedance measurements with both two-electrode cell configurations and PANI film WE at equilibrium, high-frequency distortions are generated by contribution of inductive impedance originating from instruments and wirings. Extent of distortions is found inversely proportional to the solution resistance term. In impedance measurements with conventional three-electrode cell configuration and PANI film WE kept at polarized conditions, relatively high extent of high-frequency distortions is generated by couplings between three electrodes of similar impedances. Distortions are manifested as inductive/capacitive artefact impedance, with lower inductivity and higher capacity for lower solution resistance and vice versa. Low impedance PRE is found useful for simultaneous diminishing of inductive and capacitive artefact impedances, what in some conditions could result with impedance spectra showing minor high-frequency distortions. Use of proper transfer function(s) with impedance of experimental artefacts involved, is in all cases found essential not only for determination of all parameters characterizing fast impedance response of PANI film WE, but for highlighting physical origins and possible ways of control of the content of experimental artefacts in measured impedance spectra too.