Equilibrium Fluctuation Analysis of Potassium Ferro/Ferricyanide Redox System on Platinum Disk Microelectrodes Using Field Effect Transistors

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Abstract
Spontaneous voltage fluctuations of the equilibrium potential of the ferrocyanide/ferricyanide redox couple at a Pt disk microelectrode have been measured with field effect transistors in the range of . Heterogeneous rate constants of the charge transfer reaction as well as the Warburg coefficients have been calculated from these measurements using a crossa‐correlation analysis. Stochastic and deterministic techniques for determination of electrode kinetic parameters have been compared. The deterministic procedure was a modified impedance technique in which the electrochemical system was perturbed by a lowa‐amplitude random signal applied to the electrode and the real and the imaginary parts of the equivalent electrical circuit were evaluated from the transfer function. Despite the very different nature of the origin of the signal the results obtained by these two techniques are in excellent agreement. An unusual concentration dependence of the Warburg impedance has been observed which is probably related to the small size of the electrode.

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