9312008 Takoudis This is an exploration of the utility of surface-enhanced Raman spectroscopy (SERS), in conjunction with mass spectrometry and other methods, for the in-situ molecular characterization of transition-metal surfaces involved in gas-phase catalytic reactions. In particular, the program exploits the ability to prepare ultrathin films of transition metals and other materials by electrodeposition onto gold and the fact that such films exhibit remarkably stable and intense SERS activity. This approach allows the measurement of vibrational spectra for a variety of species on transition-metal surfaces to be obtained rapidly, with high sensitivity, over a wide frequency range, at pressures of ambient or higher, and at moderately high temperatures. Coupling real-time SERS measurements with simultaneous mass-spectrometric assay of the gas-phase composition enables linking of the molecular state of the surface under working conditions with reaction rates under either transient or steady-state conditions. Initial studies are on surfaces of platinum, rhodium, ruthenium, and palladium; reactions of interest include the oxidation of carbon monoxide by nitric oxide or by oxygen, the production of dicyandiamide from ammonia and carbon monoxide, the formation of methane from carbon dioxide and hydrogen, and the oxidation of alcohols and unsaturated organics. Parallel studies using SERS and X-ray photoelectron spectroscopy or scanning force microscopy permit association of vibrational bands with surface structures. This study is devoted to the elaboration of a new method to study surface-mediated chemical processes. Although the present effort is devoted to heterogeneous catalysis, the approach should be applicable to a family of related processes, including electrochemical transformations, thin-film formation, and corrosion.
