Stability of Electrochemical Systems

Abstract

General mathematical stability conditions described in chapter “Basic Principles of Nonlinear Dynamics” are applied to electrochemical systems. The stability analysis of such systems refers to the characteristics of the entire electric circuit, and not only to the working electrode–electrolyte interface. The decisive role of the negative differential resistance (NDR), either N-shaped (N-NDR) or S-shaped (S-NDR), in the current–potential characteristics of the electrochemical process, is shown. The sources of NDR in electrode processes are listed. The linear stability analysis of one-dimensional N-NDR system indicates that under potentiostatic conditions, the electric circuit has to possess an appropriate serial resistance to exhibit bistability, while under galvanostatic conditions bistability is directly recordable without additional external resistance. For the two-dimensional electrochemical system, the criteria are derived for the occurrence of oscillations in N-NDR systems under potentiostatic conditions and it is shown the impossibility of oscillations under galvanostatic control, the latter ones being possible for the systems with hidden N-NDR region (HN-NDR type). It is shown that in the N-NDR systems, the electrode potential is an autocatalytic variable (activator), while for the S-NDR system the electrode potential is a negative feedback variable (inhibitor). For the N-NDR systems, the experimental strategy of determination of the variables essential for the oscillatory behavior is outlined.