Time resolved impedance spectroscopy as a probe of electrochemical kinetics: The ferro/ferricyanide redox reaction in the presence of anion adsorption on thin film gold

In this work, we use the time resolved technique of Fourier transform electrochemical impedance spectroscopy (FT-EIS) for quantitative kinetic analyses of Faradaic and nonfardaic, as well as heterogeneous and adsorption reactions. As a model system, we investigate the Fe(CN)63−/4− redox reaction on a thin film Au electrode in the presence of nonfaradaically adsorbing ClO4− or Cl− in neutral electrolytes. The redox process indicates a predominantly Faradaic outer sphere reaction, with nearly negligible adsorption of reactants on Au. dc voltage dependent kinetic parameters for both the anion and redox reactions are obtained by FT-EIS in real time during cyclic voltammetry. Equilibrium values of reaction rate constants, adsorption resistances and pseudocapacitances for the redox couple are also obtained. The theoretical background and working principles of these measurements are discussed, and the experimental findings are compared with previously published data.