Synchronization of Current Oscillations in Dual-Anode Dissolution System in the Presence of a Common Cathode Electrode
Authors: Hankins Michael Joseph , Wickramasinghe Mahesh , Kiss Istvan Z 
Published: February 2020

The coupling behavior of multiple working electrodes with a reference and counter electrode has been explored in several different electrochemical systems [1, 2]. Many phenomena are known to exist at far-from-equilibrium conditions such as in-phase[3, 4], anti-phase[3], and out-of-phase[5] synchronization, clustering[6], and chimera states [7, 8]. Large majority of these studies was performed in the traditional ‘three-electrode’ configuration with reference, counter, and a multi-electrode array as a working electrode. The coupling among the working electrodes typically occurs through an external resistance interface [9] or through potential drops in the electrolyte [10].
In this contribution, we explore the nonlinear dynamics of oscillatory Ni dissolution in a dual anode system; instead of the traditional reference/counter electrodes, we apply a single nickel cathode. With increasing the cathode size we see a transition from desynchronized through partially synchronized to fully synchronized behavior of the current oscillations of the anodes. The experiments thus imply that changing the cathode size affects the coupling between the anodes. Similar transition was seen when the cathode size was kept constant, but the individual resistances attached to the anodes were varied. The synchronization transitions were interpreted by the charge transfer resistance of the cathode, which inherently couples the electrodes. Further experimentation has shown that similar transitions can be seen with other cathodes (e.g., Pt, glassy carbon, and tin).
The experiments thus show that the nonlinear behavior of a complex cathode-anode cell can be greatly simplified when 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.
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