Method for determination of heterogeneous rate constants at carbon-fibre microelectrodes using multi-ac-voltammetry

A state-of-the-art FFT-instrument recently described in this journal (which measures the impedance at each dc potential applied to a working electrode) was shown to perform with excellent precision in a kinetic study at a carbon fibre microelectrode. A constant phase element (CPE) was used in a model in order to correct for double layer effects arising at the carbon fibre microelectrode (~11 mu m). This simple model in combination with the data collected by the FFT-instrument were then used in order to determine the heterogeneous rate constant for a well-defined red/ox couple. Good agreement with previously published values was obtained.