The Structure of the Metal-Solution Interface

Abstract

The electrodeposition of metals or alloys occurs within a spatial region of finite thickness at the interface (or, more precisely, an interphase) between the growing material and the solution. The structure of this region, in particular the distribution of ions, solvent molecules and other uncharged species, and the resulting distribution of electric charges and potential, has an important bearing on the interface energy of the system, the nature and rate of charge transfer processes, and on the processes of nucleation and growth of metallic crystals. In general, charge separation occurs at this interface as a result of the different nature of the mobile charges in the two regions considered: electrons in the solid and ions in the electrolytic solution. The electronic charge distribution in the electrode extends into the solution farther than the charges generated by the ionic cores, and this excess of charges must be balanced by an opposite charge in the electrolyte. In the simplest approximation this separation of charges can be thought of as a parallel arrangement of opposite charges; for this reason, this region is also called double layer.