Study of copper underpotential deposition on Au(111) surfaces

Abstract

First-principles total energy calculations are carried out to study the structure of copper underpotential deposition on Au(111) surfaces in sulfuric acid solutions. The norm-conserving method is used to construct the pseudopotentials of all the elements involved. The copper adlayer structure under various copper coverage is investigated. The results show that the proposed honeycomb structure with 2/3 monolayer copper coverage is unstable without the co-adsorption of sulfate. The co-adsorbed sulfate is found to bind to copper. The calculated structural parameters are in general agreement with those obtained from a recent X-ray experiment. In addition, the sulfate adsorption on clean Au(111) surface is studied. The results show that sulfate molecule binds much more weakly with clean Au(111) surfaces. Total energy calculations for bisulfate adsorption suggest that even though it is the dominant species in acidic electrolyte, the adsorbed bisulfate may dissociate thus leave sulfate adsorbed on the surface.