Electrochemical behaviour of Cu(II)/Cu(I) redox couple in 1-hexyl-3-methylimidazolium chloride ionic liquid

Abstract

The electrochemical behaviour of Cu(II)/Cu(I) redox couple in 1-hexyl-3-methylimidazolium chloride (C6mimCl) ionic liquid was studied using glassy carbon electrode at 375 K by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. In this electrochemical study, we have made an attempt to avoid the problem of water contamination in hygroscopic C6mimCl ionic liquid by setting the temperature at 375 K without glove box. This high temperature cyclic voltammetric study revealed two-step one electron reductions of Cu(II) to Cu(I) followed by Cu(I) to Cu metal. The reduction of Cu(II) to Cu(I) was found to be quasi-reversible at 375 K. The diffusion coefficients of Cu(II) and Cu(I), and the charge transfer rate constant of Cu(II) in C6mimCl were estimated by Randles-Ševčik equation and Nicholson’s method, respectively, and found to be consistent with the quasi-reversible process. Further, constant potential electrodeposition of metallic copper was carried out on a stainless steel electrode at 375 K and the deposit was characterised by X-ray diffraction and electron microscopy. Quasi-reversible behavior of Cu(II)/Cu(I) redox couple in C6mimCl is studied at 375 K. Diffusion and mass transport coefficients as well as charge transfer rate constant of copper species are estimated. Copper on stainless-steel electrodes by constant potential electrolysis shows island growth of Cu particles under the influence of C6mimCl.