The electrochemistry of porous lead dioxide

The reduction of. electrodeposited P-lead dioxide to lead sulphate in 5M sulphuric acid has been studied at the stationary and RDE. Potential step and sweep experiments have been made and a model for the discharge process of lead dioxide has been proposed based on charge transfer and limited high field conduction. T'he potentiostatic oxidations of lead sulphate overlying lead and lead dioxide have been investigated. The reduction behaviour of porous one-dimensional lead dioxide electrodes have been examined and shown to be independant of rotation speed in a large excess of 5M sulphuric acid. The reduction peak was broadened by the porosity. This broadening was interpreted in terms of the reaction being driven more deeply into the pore structure as the front of the electrode becomes progressively more resistive. The effect of different potential sweep rates on the current response and effects of progressive redox cycles can be fully explained on this model. The potentiostatic oxidation of porous electrodes of lead dioxide containing lead sulphate has also been investigated. The form of the current transient was found to depend on the balance of lead sulphate and lead dioxide. Investigations have been carried out on the above electrodes using the techniques of scanning electron microscopy and alternating current. Possible interpretations of the results are discussed. The influence of the solid/porous material interphase on the electrode behaviour has been investigated for a variety of alloy supports with special reference to the charge output on reduction, ease of reoxidation and electrode support/porous phase adhesion. The progress made in the understanding of some of the problems associated with the lead acid cell has been discussed.