On the influence of ionic association on the capacitance of an electrical double layer

The concept of ionic association is applied to give an explanation of the a nomalous temperature dependence of the capacitance of the electrical double layer. It is shown that, except in the intermediate region where the tempe rature derivative of the capacitance changes sign, a Bjerrum-like correctio n of the mean spherical approximation, with Ebeling's expression for the as sociation constant, satisfactorily reproduces the computer simulation data at high and low temperatures. Including polarization effects that arise fro m ionic pairs improves the description in this region. (C) 2001 Elsevier Sc ience B.V. All rights reserved.