Investigations of chemisorption and reaction at non-aqueous electrochemical interfaces by in situ surface-enhanced Raman spectroscopy

Surface-enhanced Raman scattering (SERS) spectroscopy has been successfully extended to transition metal/non-aqueous electrochemical interfaces recently in our laboratory. Some interesting and new findings are presented with the objective of illustrating the virtues of SERS as a versatile technique to examine not only aqueous but also non-aqueous interfaces. Emphasis is placed on highly catalytic roughened platinum metal surfaces. Static interfacial structure information of Pt (Ag, Au)/acetonitrile was extracted from the relevant SERS spectral features of the surface species, including interfacial trace water, the production of dissociation reactions of acetonitrile (CN-), and some effects on these spectra exerted by interfacial inorganic ions. The simultaneous competitive adsorption and reorganization processes between these interfacial species and some intentionally added small organic molecules were also systematically investigated. The important aspect of the corrosion inhibition mechanism relevant to non-aqueous media was then probed based on the success of observing SERS from non-aqueous interfaces. These included mainly widely used N- and S-containing inhibitors for iron, nickel, silver and gold. Finally, the archetypal surface catalytic oxidation mechanism of C, molecules (formic acid and methanol) on Pt group metals was investigated by using SERS combined with traditional electrochemical techniques. The non-linear vibrational Stark tuning effect of the poisoning intermediate CO and its oxidation processes are also described in comparison with experimental observations from aqueous solution and other metal surfaces. Copyright (c) 2005 John Wiley & Sons, Ltd.