Electrocatalysis of copper deposition from acid sulphate solutions by sulphite and selenite ions

Abstract

The effects of traces of chloride, sulphur, selenium and tellurium dioxide and the selenate and tellurate ions on the electrodeposition of copper from acid copper sulphate have been studied. Low concentrations of chloride have little effect on deposition kinetics but concentrations up to 20 ppm significantly affect nodule formation. Sulphur dioxide and selenium dioxide are true electrocatalysts for deposition, with SeO 2 the more effective. Molecules in solution immediately adjacent to the electrode appear to be the active catalyst. The catalytic mechanism may be a reduction oxidation cycle involving the elements in unstable forms. The chloride ion is adsorbed according to a Langmuir type isotherm. Adsorbed chloride inhibits catalysis by SO 2 and SeO 2 . The electrocatalysts have been used to demonstrate the effect of overpotential on the structure of copper deposited at constant current density.