Interaction between Ionic Liquids and a Pt(111) Surface Probed by Coadsorbed CO as a Test Molecule

• Published in: The journal of physical chemistry letters 2021-10, Vol.12 (41), p.10079-10085
• Main Authors: Eschenbacher, Roman, Schuschke, Christian, Bühlmeyer, Hanna, Taccardi, Nicola, Wasserscheid, Peter, Bauer, Tanja, Xu, Tao, Libuda, Jörg
• Format: Article
• Language: English
• Subjects: Physical Insights into Chemistry, Catalysis, and Interfaces
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.1c02983

We used temperature-programmed infrared reflection absorption spectroscopy (TP-IRAS) to study the desorption behavior of CO on Pt(111) coadsorbed with four kinds of ionic liquids (ILs), namely 1-butyl-1-methyl-pyrrolidinium-bis­(tri­fluoro­methyl­sulfonyl)­imide ([C4C1Pyr]­[NTf2]), 1-ethyl-3-methyl-imidazolium-bis­(tri­fluoro­methyl­sulfonyl)­imide ([C2C1Im]­[NTf2]), 1-butyl-1-methyl-pyrrolidinium-trifluoro-methane­sulfonate ([C4C1Pyr]­[OTf]), and 1-butyl-1-methyl-pyrrolidinium-hexafluorophosphate ([C4C1Pyr]­[PF6]). We found that CO desorbs earlier from a Pt(111) surface with coadsorbed ILs than without. In addition, the CO desorption temperature varies between different types of coadsorbed ILs, which follows the order: [C4C1Pyr]­[PF6] (365 K) > [C4C1Pyr]­[NTf2] (362 K) > [C2C1Im]­[NTf2] (352 K) > [C4C1Pyr]­[OTf] (348 K). We ascribe the difference in CO desorption temperature to the different interaction strength between ILs and the Pt(111) surface. A stronger IL–Pt(111) interaction leads to a lower CO desorption temperature. We suggest that TP-IRAS experiments of CO coadsorbed with ILs can be a useful method to aid the characterization of the interaction strength between ILs and metal surfaces such as Pt(111).