Synchronization of current oscillations in a dual-anode dissolution reaction in the presence of a common cathode electrode

Abstract

The formation of synchronization patterns are explored as a result of coupling the dual anode oscillatory nickel electrodissolution and a single cathode hydrogen ion reduction reaction in an electrochemical cell. At the onset of current oscillations, with small surface area cathode in-phase synchronization patterns were recorded, which implies the presence of coupling between the anodic reactions. As the surface area of the cathode was increased, a transition from synchronized to desynchronized behavior was observed. Similarly, the extent of synchronization and thus the coupling can be diminished with increasing the individual resistances attached to the anodes. The effect of coupling induced by the cathode was interpreted with the ratio of charge transfer resistance of the cathode to the total external resistance in the cell. The coupling effects were further demonstrated with anti-phase synchronization of relaxation, and phase and identical synchronization of chaotic current oscillations. The experimental results about the coupling effect of the cathode were also explained with a kinetic model for the reactions. The results show that the nonlinear behavior of a complex cathode-anode cell can be greatly simplified when the majority of the overpotential is due to driving the anodic reactions to a far-from equilibrium state, while the relatively simple cathode (with small overpotential and fast kinetics) acts as a coupling element between the anodes. Such simplification can be a useful tool for interpreting the complex kinetic behaviors of galvanic and electrolytic cells that have time-scale separations between the cathodic and anodic processes.