The kinetics of the Cu2+/Cu+ redox couple in deep eutectic solvents
Artikel i vetenskaplig tidskrift, 2011

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 × 10−4 cm s−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 × 10−7 cm2 s−1, respectively. The viscosity of the electrolyte was 41 ± 3 mPa s. The temperature dependency was also investigated. The activation energy of mass transfer was found to be 27.7 ± 1 kJ mol−1 and that of electron transfer 39 ± 7 kJ mol−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−. Highlights ► 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.

Impedance spectroscopy

Deep eutectic solvent

Electrochemical kinetics


Ionic liquid

Cyclic voltammetry


David Lloyd

Tuomas Vainikka

Lasse Murtomäki

Kyösti Kontturi

Elisabet Ahlberg

Göteborgs universitet

Electrochimica Acta

Vol. 56 4942-4948