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Experimental artefacts in impedance spectra measured with three-electrode cell. Polyaniline film modified Pt-working electrode case

In this paper, contributions of experimental artefacts in impedance spectra are quantitatively determined in conditions of increasing impedance of polyaniline (PANI) modified Pt electrode/0.05 mol dm-3 H2SO4, initiated at potentials of conversion of PANI film from conducting to insulating form. Impedance spectra were measured in a three-electrode cell with conventional RE(SCE) equipped with HL capillary. The model parameters describing impedance of the working electrode branch were calculated by use of the whole set-up electrical equivalent circuit involving parasitic (stray) impedances generated by presence of three electrodes and stray capacities induced between them. Comparison between the values of parameters for fits of the whole set-up EEC and these calculated without anticipation of contribution from stray impedances showed always higher parameter values of the film impedance in the second case. It seems that underestimated values of electrolyte resistance term are the main source of errors for other parameter values estimated by usual CNLS routine.

Polyaniline modified Pt electrode; Conducting to insulating conversion; Impedance spectra; Experimental artefacts

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