Revisiting cyclic voltammetry and electrochemical impedance spectroscopy analysis for capacitance measurements

The electric properties of an electrode can be evaluated by the determination of the capacitance. However, the literature reports a large panel of experimental protocols for capacitance determination, which involve either cyclic voltammetry (CV) or electrochemical impedance spectroscopy (EIS). In fact, substantial discrepancies in the assumptions are made between both techniques as in CV, the system is usually considered as ideal (and the current-scan rate relationship is assumed to remain linear at all frequencies), whereas in EIS, the system is usually considered as non-ideal and a CPE element is introduced. In this work, the electric properties of two electrode configurations, namely an Au blocking electrode and an Al electrode with a thin oxide film were investigated using EIS and CV. The capacitive domain was determined for both systems assuming the presence of an ideal and non-ideal system. The results collected from CV revealed a limited linearity between the current and scan rate for both electrode configurations. Finally, a CPE element was introduced to determine the capacitance from CV data and compared to EIS results. [Display omitted] •CV and EIS have been used for the determination of the interfacial capacitance.•CPE behaviour can be observed on both EIS diagrams and CV curves.•A Careful selection of scan-rate is critical for the analysis of CV curves.•A specific attention is required to systems with an oxide film in addition to Cdl.