Morphological aspects of the lead dioxide electrode

The technique of scanning electron microscopy has been used to observe morphological changes occurring in the redox processes involved in the interconversion of lead dioxide and lead sulphate. Observations have been made on lead dioxide films on platinum and pure lead substrates and on one and two dimensional porous lead dioxide electrodes supported either by pure lead or lead-antimony alloys. The morphology of the surfaces examined was found to be strongly affected by their history, particularly their charge/discharge cycles. Lead sulphate formed by the self corrosion process was much more porous than that formed by the electrochemical reduction of lead dioxide. For porous lead dioxide electrodes cycled to a constant response, three well defined regions were found to exist within the electrode. The oxidation of lead sulphate on lead and leadantimony alloys has shown that a duplex layer of lead dioxide existed on the lead-antimony alloys only. The primary layer of lead dioxide found on these alloys was analogous to the single layer on the pure lead electrodes. The observations of the morphological changes occurring in the two dimensional porous elect/ trodes were not consistent with the theory of the macrohomogeneous model for porous lead dioxide, possible interpretations of these results are discussed.