Surface Raman scattering of interfaces at Ag electrodes emersed from dimethylsulfoxide: Spectroscopic evidence for an emersion-induced potential shift

Surface Raman scattering has been used to study Ag electrodes emersed from LiBr solutions of dimethylsulfoxide (DMSO). Interfacial DMSO structure is generally similar to that in-situ, although spectral evidence for an emersion-induced potential shift is observed. The DMSO orientation at Ag electrodes is driven by interaction of the oxygen atom at potentials positive of the potential of zero charge (pzc) and the sulfur atom at potentials negative of the pzc. Pronounced restructuring of DMSO occurs in the vicinity of the pzc. Specific interactions between DMSO and electrolyte ions are clearly detected in the emersed interface. The observed potential shift is attributed to reorientation of the DMSO solvent dipoles at the emersed layer | gas interface. These results represent the first spectroscopic evidence for the existence of an emersion-induced potential shift.