Chapter 5 - Electric double layer at electrode interfaces

Abstract

The energy of surface atoms is known to differ from the energy of interior atoms in solids. The lattice structure of surface atoms, hence, may not be the same as that of interior atoms. Usually, surface relaxation takes place on the clean solid surface produced by cleavage. As a result of surface relaxation, the distance between the first atom layer and the second atom layer in the surface lattice becomes different from the atom–atom distance in the interior lattice. The clean surface of solids sustains not only surface relaxation but also surface reconstruction in which the displacement of surface atoms produces a two-dimensional super lattice overlapped with, but different from the interior lattice structure. Surface reconstruction on metal crystals depends on the interior lattice and on the nature of the metal. Besides metallic crystals, covalent crystals also undergo surface reconstruction. Adsorption of particles on solid surfaces may be classified into two modes: physisorption and chemisorption. In physisorption, the affinity of adsorption is small; and the lifetime of adsorbed atoms remaining on the surface is short. The configuration of physisorbed atoms tends to a close-packed two-dimensional structure. The chemisorption of electron-accepting particles, such as oxygen and sulfur, accelerates the un-reconstruction of a previously reconstructed metal surface, giving rise to a surface lattice of the same structure as the interior lattice. Coadsorption, in which two different kinds of particles are chemisorbed on the solid surface, may be classified into cooperative adsorption and competitive adsorption.