DURABILITY OF ANODIC LEAD DIOXIDE IN PRESENCE OF ELECTROACTIVE SPECIES

The durability of an active potentiostatically formed Pb O2 film was tested in connection with the nature and concentration of reductants CH3 OH, HCHO, HCOOH, KI and Fe SO4 and oxidant K2 CrO4. The electrolyte was 1.0 M H-2 SO4. The mode of breakdown was followed measuring the decay of the open circuit potential of the lead electrode. The results were interpreted in terms of: i) Competitive influences for the additive relative to the formal conversion reaction Pb O2 + 2 H2 SO4 + Pb -> 2 Pb SO4 + 2 H2O These influences are adsorbability and oxidizability of the additive. Adsorption leads to the depletion of H2 SO4 while oxidation provides an alternative pathway. ii) Redox profile of the anodic lead dioxide film. The results thus obtained reveal that HCOOH is a suitable reductant for electro-oxidation by anodic lead dioxide.