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 anomalous temperature dependence of the capacitance of the electrical double layer. It is shown that, except in the intermediate region where the temperature derivative of the capacitance changes sign, a Bjerrum-like correction of the mean spherical approximation, with Ebeling's expression for the association constant, satisfactorily reproduces the computer simulation data at high and low temperatures. Including polarization effects that arise from ionic pairs improves the description in this region. (C) 2001 Elsevier Science B.V. All rights reserved.