INTERPRETATION OF FINITE-LENGTH-WARBURG-TYPE IMPEDANCES IN SUPPORTED AND UNSUPPORTED ELECTROCHEMICAL-CELLS WITH KINETICALLY REVERSIBLE ELECTRODES

The origin of finite-length-Warburg-type impedances in supported and unsupported systems is examined within a common framework and with reference to previous exact and approximate results. While close agreement is found between an approximate treatment based on bulk electroneutrality and an exact solution of the Nernst-Planck-Poisson equation system for unsupported systems of many Debye length thickness with rapid electrode reaction kinetics, the approximate treatment is unjustified when the electrode reaction is slow or the electrode separation is less than or comparable to the Debye length.