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Anodic oxidation of cuprous sulphide in aqueous solutions Fraser, Michael J.

Abstract

The oxidation of artificial cuprous sulphide electrodes (Cu/S ratio = 1.93) was studied in acidified copper sulphate solutions in the temperature range 20 to 35° C. Rest potential measurements gave V° = 0.490 volts for the electrode or half cell potential. This is within the limits of accuracy of V° for: Cu₂S —CuS + Cu⁺⁺ + 2e V° = 0.535 + 0.13 volts The discrepancy was thought to be related to the large Cu deficien in the sulphide. In solutions with pH>4, the rest potential measurements were consistent with the following reaction: Cu₂S + 2H₂0 —CuS + Cu(OH)₂ + 2H⁺ + 2e Polarization measurements at low overpotential gave values for the following kinetic parameters: β, the symmetry factor = 1/2 λ, the number of electrons involved in each act of the rate determining step = 2 i₀, the exchange current ≈ 2 x 10-⁵ A/cm² ΔH₀*, the standard heat of activation = 26.5 kcal/mole CuS was tentatively identified as one of the reaction products. A reaction mechanism was discussed.

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