Optical and XPS evidence for the electrochemical generation of an N-heterocyclic carbene and its CS₂adduct from the ionic liquid [bmim][PF₆]

Abstract

Room temperature ionic liquids continue to be at the forefront of chemistry, covering a broad spectrum of research areas from electrochemistry and energy to catalysis and green chemistry. Therefore, it is of great value to fully understand the chemical and electrochemical reactivity and stability of ionic liquids utilized in these applications. In this context, we have investigated the electrochemical generation of an N-heterocyclic carbene and its CS 2 adduct from the ionic liquid [bmim] [PF 6 ], and X-ray photoelectron spectroscopy (XPS) proved to be a highly effective spectroscopic tool to study such systems. Initially, the dithiocarboxylate adduct was chemically synthesized as a reference compound starting from both

Probing the Dynamics of Non-Faradaic Processes in Ionic Liquids at Extended Time and Length Scales Using XPS with AC Modulation

“…In order to follow only the EDL-related processes, the amplitude of the external bias was chosen such that the Faradaic sources and possible redox reactions do not contribute to the spectral features during the experiment, but ion transport dynamics are facilitated throughout the relatively short measurement times within a few minutes. In our previous studies, we were able to identify and probe in situ redox reactions of different ILs that are imidazolium-based to form stable carbenes but only after prolonged DC excitations, up to several hours. , However, for the current study, the presence of new species or chemistries was not observed during the measurements; hence, we assume that the electrodes are ideally polarizable without significant Faradaic reactions, with the steady-state currents on the order of ∼10 nA passing through the IL drop. Accordingly, our electrochemical cell can be considered as a parallel-plate capacitor with blocking electrodes.…”

Lab-based operando x-ray photoelectron spectroscopy for probing low-volatile liquids and their interfaces across a variety of electrosystems

“…33 We, then, extended it to probing the nature of an electrochemical corrosion process between the ionic liquid and Au electrodes, 34 and finally to detect, in situ, an electrochemically generated carbene formation 35 and its CS 2 adduct. 36 Most recently, we have utilized o-XPS to probe electrowetting properties of ionic and other low-volatile liquids under both DC, 37 and AC (Ref. 38) actuations, in order to extract chemically resolved electrical information of such systems, guided by modeling.…”

X-ray Photoelectron Spectroscopy with Electrical Modulation Can Be Used to Probe Electrical Properties of Liquids and Their Interfaces at Different Stages

“…We then extended the investigation to probing the nature of an electrochemical corrosion process between the ionic liquid and Au electrodes and finally to detecting, in situ, electrochemically generated carbene formation and its CS 2 adduct . The observation of voltage-driven asymmetric ion movement through the pores of a multilayer graphene electrode was another novel application of the operando-XPS . We have recently utilized Operando XPS to probe the electrowetting properties of ionic and other low-volatility liquids under both dc and ac actuation in order to derive chemically resolved electrical information on such systems, indispensably guided by electrical modeling …”