Electrochemical behaviour of some copper(II) salts in 20 wt.% propylene carbonate+ethylene carbonate:: Standard potential of the Cu2+/Cu system at 25 °C

The behaviour of Cu(ClO4)2, CuCl2 and CuBr2 in 20 wt.% propylene carbonate (PC)+ethylene carbonate (EC) has been studied by conductivity, potentiometry and voltammetry. The conductance behavior of copper(II) halides in 20 wt.% PC+EC is explained on the basis of the equilibrium 3CuX2⇌Cu2++2CuX3 and 2CuX2⇌(CuX2)2. A copper indicator electrode in conjunction with a Hg/HgCl2(s) in 20 wt.% PC+EC reference electrode was used for the potential measurements. The results of the potentiometric measurements, combined with those of the conductance measurements, provided the standard potential, E°, of the reaction Cu2++2e−⇌Cu(s) versus SHE in 20 wt.% PC+EC at 25 °C, which is found to be 0.400±0.002 V. Sampled dc and cyclic voltammetric measurements were also undertaken with these Cu(II) salts in 20 wt.% PC+EC using Pt working and counter electrodes and Hg/HgCl2(s) in 20 wt.% PC+EC as the reference electrode. These voltammetric measurements yielded the standard potential value (0.394±0.003 V vs. SHE) of the system, which is in agreement with the value obtained by the potentiometric method.