Interfacial structure of dimethylsulfoxide at Ag electrodes from surface enhanced Raman scattering and differential capacitance

Surface enhanced Raman scattering (SERS) and differential capacitance have been used to study interfacial structure in LiBr-containing dimethylsulfoxide (DMSO) at Ag electrodes. The potential-dependent orientation of this solvent is driven by interactions of the O atoms with the Ag surface at positive potentials and by interactions of the S atoms with the surface at negative potentials. Significant spectral changes are observed at potentials in the vicinity of the pzc indicating reorientation of interfacial solvent molecules. Evidence for unique potential-dependent interactions of Li⁺ and Br^- with DMSO and trace amounts of H₂O in the electrochemical interface have been uncovered on the basis of their spectral signatures. Potential-dependent molecular pictures of the interface in this system are proposed.