Overcharging, charge reversal: Chemistry or physics?

Overcharging, also called charge reversal or charge inversion, is the occurrence of electric double layers in which, as measured by electrokinetics or interaction, there is more countercharge than charge on the surface. The trend is that the propensity of overcharging increases with the valency of the counterion. For the interpretation of this phenomenon, disparate explanations have been forwarded and elaborated that, briefly, can be distinguished as "chemical" (specific adsorption,...) and "physical" (ion correlations,...). In the present paper, an analysis of this disparity will be given. In particular, types of experiments will be proposed which can help to discriminate. (c) 2006 Elsevier B.V. All rights reserved.