On‐Surface Metathesis of an Ionic Liquid on Ag(111)

• Published in: Chemistry : a European journal Vol. 28; no. 28; pp. e202200167 - n/a
• Main Authors: Massicot, Stephen, Sasaki, Tomoya, Lexow, Matthias, Maier, Florian, Kuwabata, Susumu, Steinrück, Hans‐Peter
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 16.05.2022; John Wiley and Sons Inc
• Subjects: Anion exchanging; Anions; catalysis; Cations; Chemistry; Enrichment; Ion exchange; Ionic liquids; Metathesis; on-surface metathesis; Photoelectron spectroscopy; Photoelectrons; Silver; ultra-thin films; Vacuum; Wetting; X-ray photoelectron spectroscopy; on-surface metathesis; catalysis; ionic liquids; ultra-thin films; X-ray photoelectron spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202200167

We investigated the adsorption, surface enrichment, ion exchange, and on‐surface metathesis of ultrathin mixed IL films on Ag(111). We stepwise deposited 0.5 ML of the protic IL diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) and 1.0 ML of the aprotic IL 1‐methyl‐3‐octylimidazolium hexafluorophosphate ([C8C1Im][PF6]) at around 90 K. Thereafter, the resulting layered frozen film was heated to 550 K, and the thermally induced phenomena were monitored in situ by angle‐resolved X‐ray photoelectron spectroscopy. Between 135 and 200 K, [TfO]− anions at the Ag(111) surface are exchanged by [PF6]− anions and enriched together with [C8C1Im]+ cations at the IL/vacuum interface. Upon further heating, [dema][PF6] and [OMIm][PF6] desorb selectively at ∼235 and ∼380 K, respectively. Hereby, a wetting layer of pure [C8C1Im][TfO] is formed by on‐surface metathesis at the IL/metal interface, which completely desorbs at ∼480 K. For comparison, ion enrichment at the vacuum/IL interface was also studied in macroscopic IL mixtures, where no influence of the solid support is expected. Schematic illustration of the surface preparation: 0.5 ML [dema][TfO] and 1.0 ML [C8C1Im][PF6] were sequentially deposited on Ag(111) at 90 K. Subsequently, the sample was heated to 500 K, which leads to the selective desorption of [dema][PF6] and [C8C1Im][PF6] at ∼235 and ∼380 K, respectively. Hereby, the new IL [C8C1Im][TfO] is formed by on‐surface metathesis at the IL/metal interface, which then completely desorbs at ∼480 K.