The kinetics of the Cu2+/Cu+ redox couple in deep eutectic solvents

• Published in: Electrochimica acta Vol. 56; no. 14; pp. 4942 - 4948
• Main Authors: Lloyd, David, Vainikka, Tuomas, Murtomäki, Lasse, Kontturi, Kyösti, Ahlberg, Elisabet
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 30.05.2011; Elsevier
• Subjects: Chemistry; Copper; Cyclic voltammetry; Deep eutectic solvent; Electrochemical kinetics; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Impedance spectroscopy; Ionic liquid; Other electrodes; RTIL; Tf2N; IS; Impedance spectroscopy; ChCl; Electrochemical kinetics; Ionic liquid; Cyclic voltammetry; EMIM-Cl; RDE; DES; CV; Deep eutectic solvent; CPE; Copper; CA; Choline chloride; Ethylene glycol; Theoretical study; Electron transfer; Transition metal; Copper Compounds; Experimental study; Electrodes; Redox couple; Platinum; Eutectic; Kinetics; Chronoamperometry; Diffusion coefficient; Glycol; Electrochemical impedance spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2011.03.133

► Kinetics of Cu2+/Cu+ redox process in a deep eutectic solvent. ► Comparison of cyclic voltammetry and impedance spectroscopy. ► Diffusion coefficient of Cu+ twice that of Cu2+. ► Heterogeneous kinetics fast, transfer coefficient is 0.25. ► Activation energy of mass transfer identical to activation energy of viscous flow. Kinetics of electron transfer of the Cu(I)/Cu(II) redox couple at a platinum electrode has been studied with chronoamperometry, cyclic voltammetry and impedance spectroscopy in a deep eutectic solvent consisting of choline chloride and ethylene glycol. At 25°C, the reaction was found to be quasi-reversible with a relatively high rate constant k0 of 9.5±2×10−4cms−1, and a charge transfer coefficient α of 0.25±0.05. Diffusion coefficients for the Cu(I) and Cu(II) complexes were determined to be 2.7±0.1×10−7 and 1.5±0.1×10−7cm2s−1, respectively. The viscosity of the electrolyte was 41±3mPas. The temperature dependency was also investigated. The activation energy of mass transfer was found to be 27.7±1kJmol−1 and that of electron transfer 39±7kJmol−1. Speciation of the Cu(I) and Cu(II) complexes was determined using UV–VIS spectroscopy, and the prevailing Cu(I) complex was found to be [CuCl3]2− and that of Cu(II) [CuCl4]2−.