ADSORPTION AND ELECTROOXIDATION OF CARBON-MONOXIDE ON RHODIUM-COATED AND RUTHENIUM-COATED GOLD ELECTRODES AS PROBED BY SURFACE-ENHANCED RAMAN-SPECTROSCOPY

Surface-enhanced Raman (SER) spectra are reported as a function of electrode potential for carbon monoxide adsorbed from CO-saturated 0.0.1 M HClO4 media on thin (ca. one to three equivalent monolayer) films of rhodium and ruthenium electrodeposited onto gold. The surface state was monitored during positive-going, and subsequently negative-going, potential excursions from C-O stretching vibrations, vM-C, and surface-oxide, vM-O, vibrations. The SER results are compatible with potential-difference infrared spectra obtained under similar conditions, although the highest frequency vCO bands are apparently too weak to be detected in the latter case. The dependence of the vCO band frequencies on the rhodium, ruthenium, and also platinum and palladium films upon the electrode potential over a wide range, ca. -0.8 to 0.8 V vs SCE, is also examined by utilizing SER measurements in basic as well as acidic media.