Effects of a dc bias on electrical impedance spectroscopy in electrolytic cells

Characterization of electrolytic cells is often inferred from measurements of their electrical properties as a function of frequency by applying a sinusoidal voltage. In some cases, a dc bias is intrinsically present in addition to the ac stimulus and its effects are often neglected although they may become relevant in certain situations. As a consequence, the interpretation of the observed results might be misleading. Our aim is to estimate the influence of the bias solving numerically the Poisson-Nernst-Planck model for an electrolytic cell submitted to an ac external voltage superimposed to a bias. According to our analysis, even in the case of a small bias, the estimated Debye frequency and the low-frequency resistance of the cell are significantly influenced by it.