New hydrophobic deep eutectic solvent for electrochemical applications

Deep eutectic solvents (DESs) are known as cheap and biodegradable solvents which are easier to synthesize than ionic liquids (ILs). In this work, a new hydrophobic DES based on menthol is described. It consisted in a mixture of menthol and acetic acid in which ethanolamine has been added in order to increase the conductivity up to few mS·cm−1. The physicochemical properties as a function of temperature, in the range of 293.15 to 333.15 K, of this menthol-based DES have been compared to the ethaline, which is one of the most widely used DES. Cyclic voltammetry has been used to study the electrochemical behavior of an electroactive mediator, the hydroxymethylferrocene (FcMeOH), which is a reversible electrochemical system and its diffusion coefficient, determined in both DESs, is of the same order of magnitude than the one reported for the 1-ethyl-3-methylimidazolium bis(trifluoro-methanesulfonyl)imide (EMIMTFSI), which is the most widely used IL for electrochemical applications. This new class of DES thus provide an eco-friendly alternative for electrochemical applications.