Spectroelectrochemical Determination of Heterogeneous Electron Transfer Kinetic Parameters

Abstract

Four spectroelectrochemical approaches to the determination of heterogeneous electron transfer kinetic parameters are described. These include single potential step chronoabsorptometry for the characterization of irreversible heterogeneous electron transfer kinetics, single potential step chronoabsorptometry for the characterization of quasi-reversible heterogeneous electron transfer kinetics, asymmetric double potential step chronoabsorptometry for the characterization of both irreversible and quasi-reversible heterogeneous electron transfer kinetics, and derivative cyclic voltabsorptometry for the characterization of both irreversible and quasi-reversible electron transfer kinetics. The validity of these techniques is established for the irreversible oxidation of ferrocyanide at tin oxide optically transparent electrodes in pH 7.00 solution and for the quasi-reversible oxidation of ferrocyanide at platinum optically transparent electrodes in the same medium. The applicability of these techniques to the determination of the potential dependence of the heterogeneous electron transfer rate constants for both the reduction of horse heart ferricytochrome c and its subsequent reoxidation is demonstrated.