Surface Enrichment and Depletion Effects of Ions Dissolved in an Ionic Liquid: An X‐ray Photoelectron Spectroscopy Study

Abstract

Oberflächen ionischer Flüssigkeiten: Laut winkelabhängiger Röntgenphotoelektronenspektroskopie (XPS) weicht die Zusammensetzung einer Lösung von [Pt(NH3)4]Cl2 in der ionischen Flüssigkeit 1‐Ethyl‐3‐methylimidazolium(EMIM)ethylsulfat an der Oberfläche deutlich von der im Volumen ab. [Pt(NH3)4]2+ wird an der Oberfläche auf Kosten des EMIM‐Kations angereichert, während die Cl−‐Konzentration bis auf Werte unterhalb der XPS‐Detektionsgrenze abnimmt.

Monitoring of Liquid‐Phase Organic Reactions by Photoelectron Spectroscopy

“…This observation suggests a surface enrichment of the unreacted [ClC 4 H 8 SO 3 ] − anion at the expense of the formed chloride, which depletes into the bulk. Such a depletion of chloride has been seen before in a solution of [Pt(NH 3 ) 4 ]Cl 2 in [C 2 C 1 Im][EtOSO 3 ] and was explained by the smaller molecular volume and the lower polarizability of chloride in comparison to [EtOSO 3 ] − 22. It is noteworthy, that both IL 1 and IL 2 were free of any surface impurities, such as Si impurities from dissolved silicon grease.…”

Ionic Liquid-Modified Electrocatalysts: The Interaction of [C 1 C 2 Im][OTf] with Pt(1 1 1) and its Influence on Methanol Oxidation Studied by Electrochemical IR Spectroscopy

“…Such insights are available following an "IL surface science" approach, in which the IL layer is prepared on an atomically welldefined surface under ultrahigh vacuum (UHV) conditions [17][18][19][20][21][22][23][24]. Using a broad spectrum of techniques including, e.g.…”

Organometallic Complexes in Supported Ionic‐Liquid Phase (SILP) Catalysts: A PHIP NMR Spectroscopy Study

“…In spite of the considerable potential of the SILP immobilization technique, the present understanding of the underlying interactions at the molecular level is still underdeveloped. Recently detailed studies emerged, investigating surface and interface properties of ILs and transition‐metal complexes using X‐ray photoelectron spectroscopy (XPS) 10–12. Although XPS is inherently surface sensitive and can be applied to analyze the chemical composition in the near surface region, it is difficult to investigate SILP catalyst by this technique, especially at elevated pressures like in catalytic hydrogenation reactions.…”