The effect of Cobalt on the Kinetics of Oxygen evolution at a Lead Dioxide anode in Sulphuric Acid

Abstract

The overpotential (n)-log current density (log i) curves for the evolution of oxygen at a lead dioxide anode in 2N H₂SO₄ both in the absence and presence of cobaltous sulphate in solution have been used to determine the electrode kinetic constants α ; i₀ for a series of temperatures and also ΔH₀^*:. At 25 °C in the absence of cobalt α=O.59, i₀= 10^-11, and ΔH₀^*= 15 kcal mole^-1 When 13 mg/l cobaltous sulphate is added α= 1.0, i₀= 10^-15, and ΔH₀^*:=29 kcal mole^-1. Possible mechanisms for the reaction are discussed on the basis of these values and the rate determining steps suggested (where M represents the PbO₂ surface) are M +H₂O =MOH +H⁺ +e in the absence of cobalt and 2CoOH⁺⁺ = 2Co⁺⁺ +H₂O + O in its presence.