From frequency dispersion to ohmic impedance: A new insight on the high-frequency impedance analysis of electrochemical systems

Abstract

The increasing use of impedance for the characterization of an electrified interface is accompanied by the development of accurate models to analyze the results. In the present work, the concept of ohmic impedance is revisited using both numerical simulations and experimental results. The Havriliak-Negami equation is shown to provide a good representation of the high-frequency dispersion or complex ohmic impedance associated with the disk electrode geometry. An excellent fit to simulated complex ohmic impedance was found for both capacitive electrodes and for electrodes characterized by constant-phase-element behavior. The use of the Havriliak-Negami equation to account for the complex ohmic impedance was shown to extend the useful frequency range for regression of physical models to the impedance response for three experimental systems: a gold electrode in a 0.1 M sodium sulfate solution, an aluminum electrode in a 0.01 M sodium sulfate solution, and pure iron in a 0.5 M sulfuric acid solution.

Revisiting cyclic voltammetry and electrochemical impedance spectroscopy analysis for capacitance measurements

“…with α and Q as CPE parameters. It should be noted that the very high frequency domain shows a frequency dispersion due to the geometry of the electrode as demonstrated in different works [18][19][20][21].…”

“…In fact, the CPE behaviour is clearly distinguishable on the modified Bode representation with a constant phase angle close to 80° between 100 Hz and 2 Hz. At high frequency however, the phase angle decreases and increases due to geometry-induced current and potential distributions of the electrode, which is ascribed to the Ohmic contribution of the impedance as described in [21]. In the case of oxide films, such CPE response is attributed to a normal time constant distribution caused by variations in resistivity within the oxide film [14].…”

Impedance Response of a Thin Film on an Electrode: Deciphering the Influence of the Double Layer Capacitance

“…Thus, can represent a point‐defect [34,35] or similar [36,37] model, a passive semiconducting film, [4,38] a thin film exhibiting a resistivity distribution, [39,40] or a thin film containing active organic inhibitors [41,42] . For simplicity, the high‐frequency dispersion due to the contribution of ohmic impedance [43–46] is disregarded in this article so as to focus on the different contributions of the interfacial capacitance in the high and low frequencies.…”

Local electrochemical impedance spectroscopy: A window into heterogeneous interfaces

“…This approach has been extended by Huang et al [33][34][35] who introduced the concept of local interfacial impedance and local ohmic impedance. The latter is particularly interesting as it considers the geometry of the electrode for an improved analysis and interpretation of both local and global impedance diagrams in the high frequency domain [36].…”