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 A(1), A(2) and A(3) corresponding to the formation of PbSO4, PbO and PbO2, 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 PbO2 to PbSO4. The peak C-2 is due to the reduction of the inner PbO2 to PbO. The composite peak C-3 is due to the reduction of both PbO and PbSO4 to Pb. The plateau C-4 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. (C) 2004 Elsevier B.V. All rights reserved.