Electrochemical Impedance of Ion-Exchange Membranes with Interfacial Charge Transfer Resistances

The characteristics of the electrochemical impedance and the effect of nonlinearity on the validity of impedance measurements of ion-exchange membrane systems constituted by the membrane and two diffusion boundary layers adjacent to the membrane, including charge transfer resistances at the solution–membrane interfaces, have been investigated. Ionic transport processes are described by the Nernst–Planck and Poisson equations, while the interfacial charge transfer processes are described by means of the Chang–Jaffé equations. The electrochemical impedance and total harmonic distortion associated with the decomposition into Fourier components of the potential–time response of the system to a sine electric current have been obtained by using the network simulation method. The influence of the kinetic rate constants of the interfacial charge transfer processes on the electrochemical impedance and the linearity of the current–voltage relationship of ion-exchange membrane systems is analyzed and discussed.