Electrochemical Studies of Cu(I) and Cu(II) in an Aluminum Chloride‐N‐(n‐Butyl)Pyridinium Chloride Ionic Liquid

Abstract

A study of the Cu‐Cu(I)‐Cu(II) redox systems has been carried out in a butylpyridinium chloride‐aluminum chloride ionic liquid. Rotating disk (glassy carbon) and ring disk electrochemical studies were performed, as well as coulometric and potentiometric experiments. Cu(II) is reduced to both Cu(I) and Cu(0) in acidic (excess ) melts and the process is quasi‐reversible. Both Cu(I) and Cu(II) appear to adsorb at the glassy carbon electrodes in acidic melts. The reduction of Cu(II) appears reversible as determined by rotating disk voltammetry. In basic melts (excess butylpyridinium chloride), kinetic parameters for the slow electron transfer reduction of Cu(II) and oxidation of Cu(I) were evaluated. Both Cu(I) and Cu(II) appear to adhere to the Stokes‐Einstein equation in both acidic and basic melts, although the constancy of the viscosity‐diffusion coefficient product differs for each and changes as the melt is made either acidic or basic. Potentiometric measurements are interpreted as showing the presence of and in basic melts and perhaps and in acidic melts. Standard potentials for the various redox couples in acidic and basic melts were determined.