CURRENT TIME RESPONSES AND IMPEDANCES OF MODEL THIN-LAYER AND MEMBRANE CELLS WITH STEADY-STATE CURRENT

When electrochemical cells have symmetric bathing and symmetric electrode kinds, there are steady state currents under applied voltage steps. The impedance spectrum can be calculated in terms of steady state current and measured at each voltage. This procedure gives another method for confirming the electrochemical origins of the Rs and Cs of a system. Three example systems are analyzed and illustrated: a thin-layer cell with single charge carrier in a high concentration of supporting electrolyte; a single charge carrier in a constant resistance membrane with current controlled by coupled back diffusion of an uncharged complexing agent (a neutral carrier system) and a general liquid ion exchanger membrane with one charge carrier at dc and trapped mobile sites subject to concentration polarization, corresponding to voltage-dependent concentration profiles and distributed resistances.