Electrochemical double layer at the interfaces of Hg/choline chloride based solvents

The electrochemical interfaces of several deep eutectic solvents based on choline chloride mixtures with 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, urea or thiourea, and mixtures of acetylcholine chloride with urea were studied at a Hg electrode. The cyclic voltammetric results identified the potential domains of electrochemical stability and illustrated their dependence on the deep eutectic solvents composition. The differential capacitance-potentials, C(E), curves for the electrical double layers were obtained from electrochemical impedance data by adjusting the appropriate equivalent circuits. The structure of the interfaces is proposed to be dominated by adsorption of choline cations at large negative polarizations while at less negative or positive polarizations the structure is dominated by the adsorption of the anion. The temperature coefficients of capacitance were found to be nearly zero for Hg.