Abstract
The electrochemical behaviour of Pb electrode in aqueous Na 2SO 4 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 A 1, A 2 and A 3 corresponding to the formation of PbSO 4, PbO and PbO 2, respectively prior to oxygen evolution potential. The reverse cathodic curves show three cathodic peaks C 1–C 3 and a plateau C 4 prior to hydrogen evolution potential. The peak C 1 is related to the reduction of upper PbO 2 to PbSO 4. The peak C 2 is due to the reduction of the inner PbO 2 to PbO. The composite peak C 3 is due to the reduction of both PbO and PbSO 4 to Pb. The plateau C 4 is ascribed to the formation of PbH 2. The heights of the anodic and cathodic peaks increase with increasing scan rate, temperature and repetitive cycling. The formation of PbSO 4 layer proceeds under diffusion controlled of SO 4 2−. The formation of the inner PbO is via a nucleation and growth mechanism under charge transfer and OH − diffusion control.
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