Electrochemical behavior of novel Ti/IrOx-Sb2O5-SnO2 anodes

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-SnO2 has been shown to be among the best elecytrocatalysts for oxygen evolution. Its high stability and relatively low cost will make it more attractive than IrOx and many other electrocatalytic materials. In this paper, the open-circuit potential, voltammetric behavior, oxygen evolution mechanism, and kinetics of the IrOx-Sb2O5-SnO2 coated 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-SnO2 were somewhat different from those on IrOx, coated anodes. Apparent cathodic peaks from Ir(III)/Ir(IV) and lr(IV)/Ir(V) were observed. However, the corresponding anodic peaks were very weak. Voltammetric investigation also showed that Ti/IrOx-Sb2O5-SnO2 could provide fast electron transfer. Despite high anodic stability, severe damage occurred when a Ti/IrOx-Sb2O5-SnO2 electrode was cathodically polarized. An O-2 evolution mechanism involving cyclic formation and decomposition of =-IrO2 was proposed. The Tafel slope and partial derivativeE/partial derivativelog a(H)(+) obtained were 86 and 45 mV dec(-1), respectively.