Kinetics of the Cu(I)/Cu(Hg) electrode reaction in acetonitrile solutions of chloride ions

Abstract

The electrode reaction Cu(I)/Cu(Hg) in complex chloride solutions with acetonitrile as solvent has been investigated at the equilibrium potential by the faradaic impedance method. The ionic strength was 0.1 M with tetraethylammonium perchlorate as supporting electrolyte, and the temperature was 25°C. Differential capacity data for mercury have been determined separately, and other double-layer data have been obtained from electrocapillary measurements. From the results of the kinetic measurements at [Cu +]<1 m M, corresponding to potentials E-E ecm<−120 mV, it is concluded that the solvated Cu + as well as the complexes CuCl and CuCl 2 − take part in the charge transfer. The rate constant increases considerably on formation of CuCl. This increase can be correlated to a simultaneous, pronounced decrease in the inner-sphere solvation. The differential capacity for mercury displays a high peak at E-E ecm∼−100 mV. It is suggested that the peak could be an adsorption-desorption peak for (C 2H 5) 4N +.