Investigation of trace interfacial water at silver electrodes in a series of normal alcohols using surface enhanced Raman scattering

The behavior of trace interfacial water and its interaction with Li⁺ and Br^- ions at Ag electrodes in the series of alcohols, methanol, ethanol, propanol, butanol and pentanol is studied using surface-enhanced Raman scattering (SERS). SERS spectra in the v(O-H) region exhibit four bands from the interfacial water species which are a sensitive function of the nature of the solvent, the residual water concentration and the electrode potential. These bands are assigned to water species interacting with specifically adsorbed Br^-, Li⁺ in the outer Helmholtz plane, 'free' water species in the interface, or hydroxide in LiOH microcrystallites precipitated onto the electrode surface. Interfacial water molecules cluster around Li⁺ and Br^- ions. The spectral data suggest pronounced restructuring of the water in the interface in the vicinity of the potential of zero charge.