STABILITY STUDY AND CATEGORIZATION OF ELECTROCHEMICAL OSCILLATORS BY IMPEDANCE SPECTROSCOPY

The frequency response or impedance spectrum of an electrochemical cel l obtained under potentiostatic conditions can be used to predict the stability features of the electrochemical cell under different electri cal conditions, such as galvanostatic control for example. It is shown that the particular condition for which the system is resonant with t he perturbing signal implies the existence of a so-called Hopf bifurca tion to sustained spontaneous oscillations in the time domain. The abi lity of impedance spectroscopy to make predictions about the occurrenc e of oscillations leads in a natural way to a classification of electr ochemical oscillators into two different categories, depending on the kinetic nature of the negative faradaic impedance. The theory is illus trated by experimental and model examples.