Oxygen evolution processes

The hydrogen and oxygen evolution processes on Pb are affected by other metal additions to Pb, for example, addition of bismuth enhances both the hydrogen and oxygen evolution [127], while addition of silver inhibits hydrogen ions reduction [128]. 

Deactivation, or "passivation , behavior has been found to be a feature of the oxygen evolution process on these electrodes [284], While apparently not related to oxide dissolution, the loss of activity for oxygen evolution is evidently related to the formation of a hydrated Co-rich oxide multilayer film over a significant portion of the LaosBojCoOg electrode surface [284]. Lowering of the electrode potential restored the initial activity for oxygen evolution. Further study of this deactivation process in warranted since similar deactivation processes may occur at other oxide catalysts. 

As suggested for the OER at nickel oxide electrodes (128, 303), it is probable that high oxidation states of the Co metal ion of the oxide film or layer, on which the OER is proceeding, are involved as intermediate states (mediator sites) in the oxygen evolution processes, together with OH and O species at the surface of the oxide. A mechanistic view of the involvement of such Co metal ion species can be written (302) as follows, as for nickel oxide ... 

ELECTROCHEMICAL AND PHOTOELECTROCHEMICAL INTERPRETATION OF THE OXYGEN EVOLUTION PROCESS... 

Electrochemical and Photoelectrochemical Interpretation of the Oxygen Evolution Process 885 T. Watanabe, M. Kobayashi, T. Sagara... 

The dependence of Kolbe products on anode potential and electrode material has been the subject of considerable study. Only a few examples from recent studies will be discussed here since the interest is in mechanism determination and not electrosynthesis. Dickinson and Wynne-Jones analyzed the composition of gases evolved from acetate solutions under various conditions and their results are presented in Table 5. They also observed that with a current density of 30mA/cm in citrate and phthalate solutions, oxygen was evolved at current efficiencies of not less than 90% on the metals they examined (Pt, Ir, Pd, Au, and Ni). The results of Conway and Dzieciuch with aqueous potassium formate are seen in Table 6. These results agree with those of Dickinson and Wynne-Jones, showing that the decarboxylation reaction is almost completely inhibited by the oxygen evolution process. The anodic reaction at Pd and Au in aqueous potassium trifluoro-acetate was... 

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