Preparation of porous PbO2 electrodes by electrochemical deposition of composites

Porous Pb02 electrodes have been prepared by anodic codeposition of Pb02 particles with an electrochemically grown Pb02 matrix, with the aim of illustrating how composite deposition may be a suitable method for obtaining electrodes of large and controlled surface roughness. By exploiting the different crystal structures of Pb02, the composition of a-Pb02+; -PbO2 composites (Le. composites with an €7r matrix and a dispersed phase) has been determined by X-ray diffraction. It has been found that reliable indications on composition of deposits may be also obtained by measuring the current efficiency of the deposition process, which largely exceeds unity in the case of composites. This way, the dependence of the dispersed phase concentration in the deposits on current density and suspended particles concentration has been determined. The surface roughness of the composite electrodes has been estimated by electrochemical impedance spectroscopy. It was found to increase almost linearly with the deposition charge and reach limiting values as either the deposition current density or the suspended particles concentration are increased.