Vibrational dynamics of CO at the (100) platinum electrochemical interface

The vibrational relaxation of the CO stretching vibration when the molecule is adsorbed at a (100) platinum single crystal electrode in aqueous electrolyte is investigated by sum-frequency generation. The measured vibration lifetime of 1.5 ± 0.5 ps is in line with those previously observed for dry CO/metal interfaces. No lifetime modification upon electrode potential shift of 0.5 V could be detected. Consequently, the electrolyte or the interfacial electric field has little effect on the fast vibrational dynamics resulting from the non-adiabatic coupling of the vibration to the substrate electrons. It is speculated that the observation of a significant lifetime modification upon electrode potential shift would require non-aqueous electrolytes where the CO/Pt interface can be stable over a larger potential range.