Degradation of Ir-Ta oxide coated Ti anodes in sulfuric acid solutions containing fluoride

摘要

The lifetime of IrO2-Ta2O5 coated titanium anodes has been investigated using a galvanostatic accelerated life test (ALT) method in 2 M (2000 mol/m(3)) H2SO4 solutions containing fluoride. Fluoride addition in the concentration range of 25 - 200 ppm significantly reduces the lifetime of films through localized thinning and in some cases, complete removal of film. While the presence of fluoride does not affect the overpotential for oxygen evolution, it lowers the efficacy of oxygen evolution. Complexation of fluoride by aluminum ions reduces the deleterious effects of fluoride. Based on thermodynamic and XPS analyses, a degradation mechanism has been proposed.