Electrochemical behaviour of lead electrode in Na2SO4 solutions

The electrochemical behaviour of Pb electrode in aqueous Na2SO4 solutions (pH=6.8) has been studied by means of cyclic voltammetric and potentiostatic current–time transient techniques. The anodic polarisation profiles exhibit three well defined peaks A1, A2 and A3 corresponding to the formation of PbSO4, PbO and PbO2, respectively prior to oxygen evolution potential. The reverse cathodic curves show three cathodic peaks C1–C3 and a plateau C4 prior to hydrogen evolution potential. The peak C1 is related to the reduction of upper PbO2 to PbSO4. The peak C2 is due to the reduction of the inner PbO2 to PbO. The composite peak C3 is due to the reduction of both PbO and PbSO4 to Pb. The plateau C4 is ascribed to the formation of PbH2. The heights of the anodic and cathodic peaks increase with increasing scan rate, temperature and repetitive cycling. The formation of PbSO4 layer proceeds under diffusion controlled of SO42−. The formation of the inner PbO is via a nucleation and growth mechanism under charge transfer and OH− diffusion control.