Dual kinetic curves in reversible electrochemical systems

Abstract

We introduce dual kinetic chronoamperometry, in which reciprocal relations are established between the kinetic curves of electrochemical reactions that start from symmetrical initial conditions. We have performed numerical and experimental studies in which the kinetic curves of the electron-transfer processes are analyzed for a reversible first order reaction. Experimental tests were done with the ferrocyanide/ferricyanide system in which the concentrations of each component could be measured separately using the platinum disk/gold ring electrode. It is shown that the proper ratio of the transient kinetic curves obtained from cathodic and anodic mass transfer limited regions give thermodynamic time invariances related to the reaction quotient of the bulk concentrations. Therefore, thermodynamic time invariances can be observed at any time using the dual kinetic curves for reversible reactions. The technique provides a unique possibility to extract the non-steady state trajectory starting from one initial condition based only on the equilibrium constant and the trajectory which starts from the symmetrical initial condition. The results could impact battery technology by predicting the concentrations and currents of the underlying non-steady state processes in a wide domain from thermodynamic principles and limited kinetic information.

New Invariant Expressions in Chemical Kinetics

“…Later, Hankins et al [ 10 ] performed transient electrochemical experiments using the reduction of ferricyanide to ferrocyanide, measuring the concentration of each substance separately using a gold disk-ring electrode. The electrochemical reaction ferricyanide ⇄ ferrocyanide was approximated by a first order reversible reaction A ⇄ B.…”

Perturbed and Unperturbed: Analyzing the Conservatively Perturbed Equilibrium (Linear Case)

“…A new kinetic technique, Conservatively Perturbed Equilibrium (CPE), was analyzed theoretically in previous studies [1,2]. It is formulated within a new paradigm of chemical kinetics, the so-called "Joint Kinetics", which was developed during the last decade (see the papers [3][4][5][6][7][8] and the most recent review [9]). In a batch reactor, in the CPE experiment, the total amounts of chemical elements and the temperature are maintained constant.…”