Chemical and electrochemical kinetics of CuII reduction in chloride media

The deposition and dissolution of copper from copper sulphate solutions have been studied by galvanostatic measurements. From current overpotential relations it is concluded that the rate limiting step in the electrochemical reduction or oxidation at pH 1 is the reaction Cu2++ e ⇌ Cu+. In the presence of chloride and sulphite ions, the CuCl–2 complex is formed which stabilises the CuI state. The rate limiting step is now the reduction of this complex. Anodically the slow step is the oxidation of CuCl–2.The addition of sulphite ions chemically reduces CuII to CuI, but the rate is much slower than the electrochemical reduction at an overpotential of –100 mV.At pH 1 chemical dissolution of the copper deposited at the cathode occurs.