STUDY OF COPPER UNDERPOTENTIAL DEPOSITION ON AU(111) SURFACES

First-principles total energy calculations are carried out to study th e structure of copper underpotential deposition on Au(111) surfaces in sulfuric acid solutions. The norm-conserving method is used to constr uct the pseudopotentials of all the elements involved. The copper adla yer structure under various copper coverage is investigated. The resul ts show that the proposed honeycomb structure with 2/3 monolayer coppe r coverage is unstable without the co-adsorption of sulfate. The co-ad sorbed sulfate is found to bind to copper. The calculated structural p arameters 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 spec ies in acidic electrolyte, the adsorbed bisulfate may dissociate thus leave sulfate adsorbed on the surface. (C) 1998 Elsevier Science B.V. All rights reserved.