Surface-Enhanced Infrared Spectroscopic Study of a CO-Covered Pt Electrode in Room-Temperature Ionic Liquid

Abstract

ATR-SEIRAS is extended for the first time to study potential-induced surface and interface structure variation of a CO-covered Pt electrode in a room-temperature ionic liquid of <i>N</i>-butyl-<i>N</i>-methyl-piperidinium bis­((trifluoromethyl)­sulfonyl)­imide (or [Pip₁₄]­[TNf₂]). Owing to a wide effective potential window of [Pip₁₄]­[TNf₂], a gradual conversion from bridged CO_ad (CO_B) to terminal CO_ad (CO_L) is observed in response to positively going potentials, suggesting that [Pip₁₄]⁺ may be involved in a strong electrostatic interaction with the CO_ad. This site conversion enables the ratio of the apparent absorption coefficient of CO_L to that of CO_B to be determined. Also, the spectral results reveal the potential-dependent CO_ad frequency variations as well as the potential-induced interfacial ionic reorientation and movement at the Pt/CO/[Pip₁₄]­[TNf₂] interface