ABSTRACT
Some current issues and recent progress in utilizing infrared and especially Raman spectroscopies for the in situ vibrational characterization of adsorbates at electrochemical and related interfaces are outlined and illustrated by means of examples culled chiefly from our laboratory. The primary factors responsible for the differences in experimental strategies pursued for metal-solution interfaces compared with surfaces in gaseous and ultrahigh vacuum (UHV) environments are discussed, and the virtues of infrared reflection-absorption spectroscopy (IRAS) and surface-enhanced Raman scattering (SERS) for scrutinizing the first interfacial type are assessed. The influences of the electrochemical double layer on chemisorbate vibrational properties at ordered metal-solution interfaces as gleaned by in situ IRAS data in comparison with analogous interfaces in UHVare described, and briefly illustrated for carbon monoxide and nitric oxide on low-index Ir and Pt surfaces. The broad-based importance of the surface potential in controlling chemisorbate properties on metal surfaces is quantatively examined. The burgeoning prospects for using SERS as a versatile and uniquely sensitive vibrational probe of chemically significant, especially transition-metal, interfaces in both electrochemical and gas-phase environments are delineated. Illustrative examples include elucidating aromatic chemisorbate bonding and the reactive nature of surface oxides.
