Inactivation of PbO2 Anodes during Oxygen Evolution in Sulfuric Acid Solution

Ti-substrate PbO2 (Ti/PbO2) anodes with Sb-doped SnO2 interlayer were prepared by thermal decomposition-electroplating technique. The behavior and mechanism of the inactivation of Ti/PbO2 anodes were studied by the accelerated life test, electrochemical impedance spectrum, XRD and SEM-EDX. The results showed that the inactivation of Ti/PbO2 anodes was a developing process. During oxygen evolution, partial active oxygen atoms produced as intermediate product diffuse toward Ti substrate, and they oxidize Pb3+ to Pb4+ in the PbO2 coating to occupy gradually the oxygen vacancies as free electron donors. This resulted in not only the decrease of conductivity but also a change of intrinsic stresses from tensile stresses to compressive stresses. When the process was finished on the whole, large numbers of active oxygen atoms began to diffuse to Ti substrate. The oxidation of Ti substrate led to the production of an interfacial stresses. Under the effects of compressive intrinsic stresses and interfacial stresses, PbO2 coating knobs out, subsequently flakes off and Ti/PbO2 anodes become inactive rapidly.