Characterization of water structure on silver electrode surfaces by sers with two-dimensional correlation spectroscopy

Surface-enhanced Raman scattering (SERS) spectra were collected continuously during cyclic voltammetric measurements on silver electrodes in alkaline aqueous solution at room temperature. Three water librational modes as well as the bending mode peak were observed in cathodic potential range. The 2D-COS analysis of spectra collected in LiOH and KOH solutions showed that the librational bands appear prior to the bending band on the cathodic scan, while in CsOH solution the potential dependence of these bands was identical. A comparison of librational band frequencies revealed that the water molecules around Cs+ cations arranged on the electrode surface were poorly hydrogen bonded in contrast to Li+ and K+. The water bending band of spectra collected in LiOH solution was found to be the convolution of two contributions, consistent with a two state model of water arranged on an electrode surface.