Numerical investigations of solution resistance effects on nonlinear electrochemical impedance spectra

The effect of solution resistance on the nonlinear electrochemical impedance spectra under quasi-potentiostatic conditions was investigated by numerical simulations. An electron transfer reaction, a reaction with an adsorbed intermediate and a reaction exhibiting negative resistance were chosen as the candidates and large amplitude perturbations were employed. The potential across the interface drifts initially and stabilizes after a certain time, which depends on the solution resistance and the kinetic parameter values. The fraction of the applied potential drop occurring across the metal-solution interface depends on the frequency and the amplitude of the perturbation as well as the value of solution resistance. This in turn leads to the possibility that, for a given conditions, a part of the spectrum may be acquired in the linear regime while the remaining part may be acquired in the nonlinear regime. The sensitivity of the Kramers Kronig transform (KKT) to identify these cases is evaluated. The results show that although the spectra are distorted by poorly conducting solution, the sensitivity of KKT to identify the nonlinear effects is not enhanced by the introduction of significant solution resistance.