Lattice-Gas Models of Adsorption in the Double Layer

The theory of statistical-mechanical lattice-gas modeling of adsorption is reviewed and shown to be applicable to a range of electrochemical problems dominated by effective, lateral adsorbate--adsorbate interactions. A general strategy for applying the method to specific systems is outlined, which includes microscopic model formulation, calculation of zero-temperature phase diagrams, numerical calculation of thermodynamical and structural quantities at nonzero temperatures, and estimation of effective, lateral interaction energies that cannot be obtained by first-principles methods. Phenomena that are discussed include poisoning and enhanced adsorption, and illustrative applications to specific systems are reviewed. Particular problems considered are: the poisoning by sulfur of hydrogen adsorption on platinum (111), the electrochemical adsorption of naphthalene on polycrystalline copper and of urea on single-crystal platinum (100), and the underpotential deposition of copper on single-crystal gold (111).