High Frequency Faradaic Rectification Voltammetry at Microelectrodes

Abstract

An experimental setup for carrying out faradaic rectification measurements at micrometer-sized electrodes under potential control is described. A new method of data analysis is proposed that allows the determination of the standard rate constant and the electron-transfer coefficient of a fast charge transfer process without knowing the impedance of the microelectrode. This method is based on the frequency dependence of the shape of the faradaic rectification voltammograms (i.e., the average width of the peaks and the ratio of the peak heights) rather than on the magnitude of the faradaic rectification signal. The method was tested in the determination of heterogeneous electron transfer kinetics of Fe(CN)₆^3-/4- and Ru(NH₃)₆^2+/3+ in aqueous solutions on a platinum microelectrode (12.5 μm in radius) and ferrocene/ferrocinum redox couple in a dimethylformamide solution on a gold microelectrode (12.5 μm in radius).