Comparison of Approaches for Assessing Linearity of Impedance Measurements

Abstract

Electrochemical impedance spectroscopy experiments are inherently nonlinear for systems affected by faradaic reactions. The methods used to determine whether an experiment is sufficiently linear include observation of current as a function of potential, known as Lissajous plots, measurement of total harmonic distortion, and post-experiment assessment of consistency with the Kramers-Kronig relations. An experimental approach is employed to compare sensitivity of these methods to determination of nonlinear response in electrochemical impedance measurements. The Lissajous figures showed linear behavior for a total harmonic distortion equivalent to 1 percent of the fundamental; whereas, the measurement model analysis revealed nonlinear behavior only for larger perturbation amplitudes.