Lead dioxide electrodes for high potential anodic processes

Abstract

Doping of PbO2 by cations (Fe3+, Co2+ and Ni2+), by F- and by cations and F- simultaneously is discussed as a way of improving the stability and electrochemical activity in processes occurring at high potentials. Doping allows the control of the amount of structural water in an oxide. Radiotracer experiments showed that high electrodeposition current densities favour the segregation of incorporated tritium (protons) at the surface. On the other hand, fluorine doping results in a marked decrease in the amount of surface oxygen species. The influence of doping with metal cations strongly depends on the nature of the metal. Iron behaves like fluorine, while nickel causes an accumulation of surface oxygen species. Doped PbO2 electrodes have quite good activities for the electrogeneration of ozone. In particular, Fe and Co doped PbO2 showed a current efficiency of 15-20%for this process. This result is relevant to our recent studies on ?cathodic oxidation?, i.e., an ozone mediated electrochemical method in which an O2 stream is used to sweep theO2/O3 gas mixture produced at a PbO2 anode into the cathodic compartment of the same electrochemical cell containing polluting species.