Electrochemical behavior of novel Ti/IrO_x-Sb₂O₅-SnO₂anodes

There are growing interests in anodes for oxygen evolution because of the importance of this reaction in many electrochemical processes such as water electrolysis, electroplating, electrosynthesis, metal electrowinning, and electroflotation. Ternary IrOx-Sb2O5-SnO2has been shown to be among the best elecytrocatalysts for oxygen evolution. Its high stability and relatively low cost will make it more attractive than IrOxand many other electrocatalytic materials. In this paper, the open-circuit potential, voltammetric behavior, oxygen evolution mechanism, and kinetics of the IrOx-Sb2O5-SnO2coated titanium anodes were studied. It was found that the open-circuit potential could change significantly during the initial period of time probably because of the hydration of the coating film. Cyclic voltammograms obtained on Ti/IrOx-Sb2O5-SnO2were somewhat different from those on IrOxcoated anodes. Apparent cathodic peaks from Ir(III)/Ir(IV) and Ir(IV)/Ir(V) were observed. However, the corresponding anodic peaks were very weak. Voltammetric investigation also showed that Ti/IrOx-Sb2O5-SnO2could provide fast electron transfer. Despite high anodic stability, severe damage occurred when a Ti/IrOx-Sb2O5-SnO2electrode was cathodically polarized. An O2evolution mechanism involving cyclic formation and decomposition of ≡IrO2was proposed. The Tafel slope and ∂E/∂log aH+obtained were 86 and 45 mV dec-1, respectively.