Theory of Square-wave Voltammetry of two Electrode Reactions Coupled by Reversible Chemical Reaction

An ece mechanism in which chemical reaction is permanently in equilibrium isinvestigated theoretically. the calculations were performed by the method of numericalintegration for fast and reversible electrode reactions as well as for the reactions that arecontrolled by the electron transfer kinetics. in square-wave voltammetry the responsedepends on the difference in standard potentials of individual electron transfers and on thedimensionless equilibrium constant of the chemical reaction. depending on the concentrationof compound x-, which is one of reactants in chemical reaction, either a single peak or thesplit response may appear. in the first case the peak potential depends linearly on thelogarithm of x- concentration, with the slope -2.3rt/2f. the potential of the first peak of thesplit response is also linear function of, but the slope is -2.3rt/f. the relationship isdetermined between standard potentials and the critical value of the equilibrium constantabove which the response splits in two peaks. under the influence of electrode kinetics, theresponses change with square-wave frequency. the first electron transfer is slow and thesecond one is fast if two peaks appear at the lowest frequency and merge into a single peak atthe highest frequency. if the second charge transfer is slower that the first one, the differencein peak potentials increases with the increasing frequency.