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, propa nol, butanol and pentanol is studied using surface-enhanced Raman scatterin g (SERS). SERS spectra in the nu(O-H) region exhibit four bands from the in terfacial water species which are a sensitive function of the nature of the solvent, the residual water concentration and the electrode potential. The se bands are assigned to water species interacting with specifically adsorb ed Br-, Li+ in the outer Helmholtz plane, "free" water species in the inter face, or hydroxide in LiOH microcrystallites precipitated onto the electrod e surface. Interfacial water molecules cluster around Li+ and Br- ions. The spectral data suggest pronounced restructuring of the water in the interfa ce in the vicinity of the potential of zero charge.