Discontinuous immittance due to a saddle node bifurcation I: 1-, 2- and 3-part immittance diagrams

The Frumkin isotherm for the electrosorption reaction is S-shaped for the interaction parameter values lower than a critical level, leading to a hysteresis loop during steady-state studies. It is shown that isotherm branch switching phenomena can occur during the study of the electrosorption reaction by electrochemical impedance spectroscopy. Two- and three-part discontinuous impedance diagrams can be observed when the sinusoidal potential modulation spans the discontinuity potentials, depending on the frequency sweep direction. (C) 1998 Elsevier Science S.A. All rights reserved.