Electrochemical Processes at the Interface between Two Immiscible Organic Solvents

The ongoing importance of the liquid/liquid phase boundary means its structure and reactivity continues to attract attention. This attention is usually focussed on the water/organic interface, although many other pairs of immiscible liquids exist. Water/organic interfaces have been studied electrochemically because of the ability to polarize this interface. Here we report a water-free “all-organic” Interface between Two Immiscible Electrolyte Solutions (ITIES) formed from ethylene glycol and α,α,α -trifluorotoluene. This interface is found to exhibit a polarizable potential window of 0.34 V, thereby allowing direct investigation of ion transfer (IT) and electron transfer at this new water-free interface. The effect of water addition to the ethylene glycol phase, on the polarizable potential window and transfer energy of tetraethylammonium ions, is also investigated. We also report the first voltammetric studies of spontaneous, yet kinetically slow, electron transfer behaviour of the Cu2+/Cu+ and Fe3+/Fe2+ redox couples at the water-free interface. Additionally, we examine spontaneous deposition of noble metals at this interface and explore examples of other all-organic ITIES systems, combining ethylene glycol with other conventional organic solvents used in liquid/liquid electrochemistry.