Bi-doped PbO2 anodes: Electrodeposition and physico-chemical properties

The influence of bismuth ions on kinetics of lead dioxide electrodeposition from methanesulfonate electrolytes and physico-chemical properties of obtained coatings were studied. Experimental results are consistent with a mechanism previously proposed in the literature for lead dioxide electrodeposition. The presence of bismuth ions in the electrodeposition solution causes a decrease of rate constants of lead dioxide formation due to co-adsorption phenomena. Deposits from solutions containing bismuth ions appear shiny dark grey, and show good adhesion to metal support. SEM images reveal a compact structure with spindle-shaped submicron and nanosized crystals and X-ray diffractograms demonstrated that incorporation of bismuth diminishes the size of crystal particles. Oxygen evolution was investigated to test electrocatalytic activity. It is shown, that oxygen overpotential on modified electrodes is significantly higher than on non-modified PbO2-electrode, which depends on bismuth content in deposit and segregation of bismuth that induces surface heterogeneity due to sites with different electroactivity for water oxidation.