Ions at Solid-Liquid Interfaces

Introduction

In this entry the charge distribution at the interface between solids and electrolyte solutions is considered. Experience has shown that, unless special precautions are taken, the solids acquire a surface charge. An equal but opposite charge accumulates in the solution, adjacent to the solid. Thus, an electric double layer is formed. This double layer formation is a spontaneous process. Relevant questions include “What is the driving force?” “What can be measured?” and “What is the structure of the double layer?” We shall emphasize strong electrolytes and aqueous systems because there the basic features are most pronounced and because such systems are relevant for practice.

As a whole, electrolyte solutions are electroneutral. They contain equal amounts of cationic and anionic charges. Thermodynamically they consist of water and one, or more, dissolved electroneutral electrolytes, which can be acids, bases, and/or salts. The distribution of ions in solution is not random;...