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

► 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.