The influence of electrolyte media on the deposition/dissolution of lead dioxide on boron-doped diamond electrode – A surface morphologic study

A comparative study of the electrodeposition/dissolution of PbO2 in acidic, neutral and basic media was carried out on boron-doped diamond (BDD) electrode using cyclic voltammetry (CV) and scanning electron microscopy (SEM). A single redox peak was observed in the CV for 1 mM of Pb2+ in nitric acid solution on the BDD electrode. Both anodic and cathodic peak potentials were found to shift in the negative direction with increasing pH. A plot of pH vs. cathodic peak potentials led to a slope value of 122 mV indicating the involvement of two electrons and four protons in the electrochemical process. In the neutral medium, two redox couples were observed in the voltammogram. Further change from neutral to alkaline pH resulted in the merging of these two redox couples, followed by their disappearance at a pH value of 11.4. Instead, a new anodic peak was noted in the voltammogram at this pH. In strongly alkaline medium, the increase in the net peak current on both the anodic and cathodic sides was correlated with the chemical dissolution of PbO2 nuclei in addition to the electrochemical dissolution. From the SEM image, it is observed that the structure and morphology of the electrodeposits obtained on BDD electrode were strongly influenced by the electrolyte media based on a range of pH values.