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 s ulfuric acid solution has been investigated in-situ by SERS spectrosco py as a function of solution chloride concentration and electrode pote ntial. In solutions containing low concentrations (less than 10 ppm) o f chloride, the adsorption of sulfate and chloride species at the copp er electrode is potential dependent. At low cathodic overpotentials, c hloride is the predominant adsorbed species, while at high cathodic ov erpotentials, chloride is displaced by SO42- ions as the adsorbed spec ies at the electrode surface. In electrolytes containing greater than 20 ppm chloride, the halide ion is the predominant adsorbed species ov er the entire potential range investigated. However, the presence of s pectral bands associated with adsorbed SO42- ions are still evident, t hus implying the presence of sulfate as a secondary adsorbed species.