Fourier Transformed Large Amplitude Square‐Wave Voltammetry as an Alternative to Impedance Spectroscopy: Evaluation of Resistance, Capacitance and Electrode Kinetic Effects via an Heuristic Approach

Abstract

Abstract A detailed simulation of Fourier transformed large amplitude square‐wave voltammetry is presented in the frequency domain for the process Red⇌Ox+e − . The simulation takes into account the influence of the electrode kinetics (Butler–Volmer model), uncompensated resistance ( R u ) and double layer capacitance ( C dl ). Of particular significance is the prediction that the even harmonic responses are only detected in the presence of quasi‐reversibility or uncompensated resistance, and also are essentially devoid of charging current. In contrast, the DC and odd harmonic AC components exhibit much larger faradaic currents and also contain charging current. Conveniently, detailed analysis of the simulated DC and AC harmonic components reveals the presence of readily recognised patterns of behaviour with unique levels of sensitivity to electrode kinetics, R u and C dl , that facilitate quantitative analysis of these terms. These electrochemical parameters are generally calculated by small amplitude impedance spectroscopy and utilisation of linear analysis of equivalent circuits. Experimental studies on the one electron oxidation of ferrocene in dichloromethane (0.1 M Bu 4 NPF 6 ) and the one electron reduction of [Fe(CN) 6 ] 3− in aqueous 0.5 M KCl electrolyte analysed via heuristic forms of data analysis based on recognition of patterns of behaviour, are presented as examples of a reversible process with significant uncompensated resistance and a quasi‐reversible process with minimal ohmic drop, respectively. Results demonstrate the advantages of a more intuitively implemented form of data analysis than presently available with conventional forms of impedance spectroscopy.