Nonlinear Frequency Response Analysis of the Ferrocyanide Oxidation Kinetics. Part II. Measurement Routine and Experimental Validation

Abstract

Kinetics of ferrocyanide electrooxidation was investigated by nonlinear frequency response analysis (NLFRA) of current output to the sinusoidal large-amplitude potential perturbation input. The aim was to establish a measurement routine and to validate experimentally the NLFRA method on an example of a simple electrochemical reaction comprising charge and mass transfer. The first-order frequency response function (FRF) contains quasi-linear information on the reaction kinetics and corresponds to electrochemical admittance. The nonlinear fingerprint of the system is contained in the second-order FRF. The first- and second-order FRFs are determined from experimental first and second harmonics. Their intensities depend on the input signal amplitude, which has to be chosen carefully to avoid the contributions of higher order harmonics. The influence of the potential and electrode rotation speed on the first- and second-order FRFs has been studied. The experimentally obtained FRFs are compared with the theoretical FRFs determined in Part I of this work. The theoretical FRFs can predict all essential experimental observations. These findings indicate that additional information on reaction kinetics can be gained from the analysis of the second-order FRF.