Adsorption of CO 3 on a silver electrode in Na 2CO 3 solution studied by SERS

Abstract

In-situ surface enhanced Raman study has been made for CO 3 2− adsorbed on a silver electrode in 0.5M Na 2CO 3 solution. CO 3 2− is chemisorbed on the electrode surface in monodentate AgOCO 2 or ▪ , prior to the formation of the anodic film and after reduction of the film. The chemisorbed CO 3 2− is observed above about −0.3 V versus SCE in the anodic potential sweep and it disappears at about −0.6 V versus SCE in the cathodic scan. Potential dependences of the vibrational frequencies indicate that as the potential is scanned more anodic the AgO bond becomes stronger and the force constant between the carbon and free oxygen atoms increases, whereas the bond between the carbon and oxygen bridging carbon and silver is weakened. By SERS, we have observed an interchange of ion species at the electrode surface between CO 3 2− and Na + hydrated by water molecules around the potential of zero charge. The vibrational frequency of those interfacial CO 3 2− ions is different from that of the free ions in the solution.