ON THE DETERMINATION OF DISTRIBUTED DOUBLE-LAYER CAPACITANCES FROM COLE-COLE PLOTS

The solid/liquid interface can often be modeled by the familiar equiva lent circuit consisting of a solution resistance in series with a para llel combination of the double-layer capacitance C and the resistance to charge transfer R(p). For this model, when plots of the imaginary p art vs the real part of the complex impedance produce depressed semici rcles (Cole-Cole plots), the centers of which lie below the real axis, then the relaxation time of the equivalent RC circuit is distributed around a most probable value tau(0) = CR(p), with the degree of depart ure from ideality given by an appropriate parameter alpha. Four method s are developed to calculate C and alpha from Cole-Cole plots, and the se methods are illustrated both for model systems and experimental dat a. Published by Elsevier Science Ltd.