Effect of chloride anions on Cu electrodeposition onto Pt(110) and Pd(110)surfaces

Cyclic voltammetry for Cu UPD on Pd(110) in H2SO4, HClO4 and in Cl- contain ing solutions has been studied in comparion with Cu UPD on a Pt(110) surfac e. The structural properties of Pd(110) and Pt(110) after Cu UPD in differe nt electrolyte solutions were investigated by LEED, RHEED and Auger electro n spectroscopy. Structural models for Pd(110) covered by 1 and 2 ML Cu, der ived from the coulometric charge, AES measurements and the diffraction data are presented. Specific adsorption of SO42-/HSO4- anions causes the formation of ordered c (2 x 4) and c(2 x 2) structures on Pt(110) and Pd(110) respectively. In the presence of chloride ions, specific adsorption of Cl on the Cu/Pd(110) sur face gives rise to a pronounced change in the voltammogram and results in t wo ordered superstructures, while on Pt(110) no specific adsorption of Cl t akes place.