Dependence of surface enhanced Raman scattering of water on the hydrogen evolution reaction

Surface enhanced Raman scattering (SERS) of water with abnormal enhancement of the bending and libration modes can be detected at potentials where hydrogen evolution is occurring over Cu and Ag electrodes. The SERS intensity is critically dependent on the current density and hence related to the dissociation of water. The result infers that the interfacial water undergoing dissociation could possess a special structure involving a partially broken hydrogen bond and hence a corresponding intermediate electronic state. We suggest it is necessary to reconsider and modify existing SERS mechanism(s) to explain these results on reactive molecules undergoing surface reaction processes.