Electron transfer mediated by redox polymer electrodes: Theory for rotating disc voltammetry with transfer at the film-solution interface and reversible electrode-coating reaction

Abstract

A theoretical study of electron transfer, mediated by a redox polymer electrode, to a species in solution, is presented for the rotating disc voltammetric method. The transfer occurs at the film—solution interface, and the electron exchange between the redox polymer and the electrode is assumed to be reversible. The case of a reduction is considered. The voltammograms are similar to those obtained at a bare electrode. When the redox potential of the system in solution, E 2 0, is more positive than that ( E 1 0) of the system in the redoxpolymer, the transfer is always possible, but it occurs at potentials at most 0.25 V more positive than E 1 0. When E 2 0< E 1 0 on the contrary, the transfer is possible only if E 1 0- E 2 0 is smaller than about 0.3.V. The current can be limited by diffusion in solution, diffusion in the coating or by the heterogeneous reaction at the film solution interface. Variations of the limiting current with the rotation rate or the concentration in solution are studied; a limit can be reached in certain cases. Application to the study of experimental examples are discussed.