In situ X-ray absorption spectroscopy study of copper under potential deposition on Pt(111) : role of the anions on the Cu structural arrangement

International audienceCu UPD on Pt(111) has been studied by XANES and EXAFS in the fluorescence mode, under grazing and normal X-rays incidence, in two electrolytic mediums (sulfate solution and chlorine one). For a complete deposited Cu monolayer, with SO42− anions, oxygen atoms in atop site with respect to copper atoms are detected clearly. The Cu–Cu interatomic distance deduced from EXAFS calculations is smaller than the Pt–Pt distance, 2.68 Å instead of 2.77 Å, while quantitative XANES data analysis is coherent with an epitaxial growth of Cu on Pt(111). We conclude that Cu full layer is composed of bidimensional domains, with (1×1) and threefold hollow sites. In presence of chloride anions, oxygen atoms are replaced by chlorine ones, providing a (√3×√3)R30° superstructure, while copper atoms adopt the same (1×1) and threefold hollow sites configuration.