Interactions Between the Room-Temperature Ionic Liquid [C₂C₁Im][OTf] and Pd(111), Well-Ordered Al₂O₃, and Supported Pd Model Catalysts from IR Spectroscopy

Abstract

The interactions between ionic liquids and their supports determine many of their applications. The adsorption of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C 2 C 1 Im][OTf] on Pd(111), ordered Al 2 O 3 /NiAl(110), and Pd nanoparticles supported on Al 2 O 3 /NiAl(110) was investigated under ultrahigh vacuum (UHV) conditions using time-resolved infrared reflection absorption spectroscopy (TR-IRAS). On Pd, the [OTf] − anion stands up with its CF 3 group directed toward the vacuum, whereas the anion is less clearly oriented on the oxide. We also find that strong interactions of the IL with the Pd result in migration of the IL from the oxide to the metal nanoparticles.