Electrochemical cell with the reversible electrode–solid electrolyte or ionic melt interface in galvanodynamic and potentiodynamic operating modes

Resumo

This work is aimed at studying the kinetics of the following two simultaneous processes: charging of the double electrical layer and the charge transfer at the reversible silver electrode–sulfate solid electrolyte or corresponding ionic melt interface in two operating modes of electrochemical cell, namely, galvanodynamic and potentiodynamic ones. The electrochemical kinetics has been studied by the method of operational impedance based on the Ohm law of interaction between Laplace transformed current, voltage, and complex resistance (impedance). Using appropriate mathematical calculations, analytical expressions are obtained for the current passing via a cell during linear potential scanning (potentiodynamic mode) as a function of time and for the interface potential as a function of time in the galvanodynamic mode (linear current scanning). The time dependence of the potential of the electrode–solid electrolyte or ionic melt interface is described by an exponential function in the potentiodynamic mode of the cell operation. An analysis and comparison of the results of the two independent electrochemical modes demonstrate that the behavior of the electrochemical cells containing a reversible metallic electrode, i.e., a solid electrolyte or the corresponding ionic melt, obeys the classical Randles–Ershler equivalent circuit. This statement can be proved by both the alternating current method (impedance method) and relaxation galvanodynamic and potentiodynamic methods (linear scanning of potential and current).