A SERS study of SO42-/Cl- ion adsorption at a copper electrode in-situ

The adsorption of chloride and sulfate ions at a copper electrode in sulfuric acid solution has been investigated in-situ by SERS spectroscopy as a function of solution chloride concentration and electrode potential. In solutions containing low concentrations (less than 10 ppm) of chloride, the adsorption of sulfate and chloride species at the copper electrode is potential dependent. At low cathodic overpotentials, chloride is the predominant adsorbed species, while at high cathodic overpotentials, chloride is displaced by SO42- ions as the adsorbed species at the electrode surface. In electrolytes containing greater than 20 ppm chloride, the halide ion is the predominant adsorbed species over the entire potential range investigated. However, the presence of spectral bands associated with adsorbed SO42- ions are still evident, thus implying the presence of sulfate as a secondary adsorbed species.