Potential Response of Lead Dioxide/Lead(II) Galvanostatic Cycling in Methanesulfonic Acid: A Morphologico-Kinetics Interpretation

Abstract

In the light of electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and Potential vs. Time responses analysis, a new interpretation of the evolution of a lead dioxide (PbO2) electrode potential during PbO2(s)/Pb2+(aq) galvanostatic cycling in methanesulfonic acid is proposed. This interpretation relies on the morphological changes of the PbO2 surface highlighted by SEM images and the double layer capacitance evaluation. It is likely that these surface changes alter the specific surface area of the layer and therefore the local current density of the PbO2 deposition/dissolution reactions. In particular, it has been found that a high porosity is created during the first part of the second deposition step and in the subsequent deposition steps of cycling, which can explain the low polarization associated with these periods. This porosity most probably remains encapsulated in the layer when more PbO2 is deposited. It is then released during the following dissolution periods, which again affects the electrode potential by decreasing the polarization.