PROBING ELECTRODE ELECTROLYTE INTERFACIAL STRUCTURE IN THE POTENTIAL REGION OF HYDROGEN EVOLUTION BY RAMAN-SPECTROSCOPY/

The detailed interfacial structure in the potential region of severe h ydrogen evolution, to date, is far from clear due to lack of both expe rimental data and correlated theoretic models. It has been shown that it is possible to surmount, to some extent, the disturbance of the spe ctroelectrochemical measurement by strong hydrogen bubbling in the pot ential region of severe hydrogen evolution by using a surface enhancem ent effect and a thin-layer cell configuration. Using this approach, w e have obtained surface enhanced Raman scattering (SERS) spectra of wa ter at an Ag electrode at very negative potentials at various concentr ations of NaClO4. To explain the abnormal reversal of the peak intensi ty ratio of the bending to the stretching vibration, a preliminary mod el of the electrode/electrolyte interface is presented. The water mole cule is oriented with one hydrogen attached to the surface and the oxy gen towards an adsorbed cation which is partially dehydrated owing to the very strong electrostatic force. Raman spectra of hydrogen bound a t a Pt electrode in solutions of varying pH from 0 to 14 at potentials of mild hydrogen evolution have also been presented for the first tim e. The spectra reveal that the Pt-hydrogen interaction is influenced b y both the potential and the interfacial structure. These primary stud ies may initiate more molecular-level research of electrochemical inte rfaces in the potential region of hydrogen evolution.