Electrochemical Reactions with Consecutive Charge-Transfer Steps: Steady-State and Time-Dependent Behavior under Charge-Transfer and Diffusion Control

Abstract

Electrochemical reactions involving consecutive charge‐transfer steps as expressed by the reaction schema Sv=Sv+1+zve− v=1,2,…,n are considered assuming that the only irreversible processes are charge‐transfer and diffusion and that disproportionation of the intermediate reaction products does not occur. An arbitrary number of n consecutive steps is assumed where feasible, but detailed discussion is restricted to the experimentally best understood case of a two‐step reaction. A general description is given of the steady‐state current density‐overvoltage characteristics and for the current density vs. time curves in potentiostatic single‐pulse experiments and for the variation of overvoltage with time in galvanostatic single‐pulse experiments, respectively.

Two-Electron Transfer Reactions in Electrochemistry for Solution-Soluble and Surface-Confined Molecules: A Common Approach

“…Thus, it has been shown that, with the appropriate normalization in each case, the electrochemical signal obtained when normal pulse voltammetry (NPV) is applied in the case of solution soluble species for electrodes of any geometry and size is coincident with the charge transferred-potential one for surface-confined systems in any electrochemical technique. Thus, their derivatives lead to a common normalized peak-shaped voltagram in derivative normal pulse voltammetry (dNPV), for solution soluble molecules, ,,,− and in cyclic voltammetry (CV), for surface-immobilized ones. ,,− ,− These normalized responses are only potential-dependent as a consequence of the reversible behavior of the process, which is reflected in the independence of time of surface concentrations (solution phase case) ,− and excesses (immobilized species). − …”