Vibrational dynamics of CO at single-crystal platinum electrodes in aqueous and non-aqueous electrolytes

The vibrational dynamics of CO at two electrochemical interfaces is studied as a function of the electrode potential, for CO/Pt(100) in 0.1M aqueous H2SO4 and CO/Pt(110) in 0.05M C16H36ClNO4 acetonitrile electrolyte. The measured lifetime of similar to 1.7 ps is in line with those previously determined for dry CO-metal interfaces. The lifetime appears to be independent of the electrolyte composition, and unaffected by an electrode-potential variation as large as 2 V achieved for the non-aqueous electrolyte experiment. These measurements suggest that the 2 pi* CO acceptor orbital involved in the substrate/adsorbate charge transfer process is much broader than 0.8 eV.