Electrochemical surface characterization of IrO2-Ta2O5 coated titanium electrodes in Na2SO4 solution

The surface characterization of IrO 2 -Ta 2 O 5 coated titanium electrodes has been studied in a 0.5 mol dm 3 Na 2 SO 4 solution using cyclic voltammetry. The results showed that the surface state of all the electrodes is controlled by the redox transition of Ir(III)/lr(IV). The voltammetric charge, the double-layer capacitance, and the electrochemical activity present similar variation with the composition of the oxide mixture, showing maximum values at 50-70% lr. The high electrochemical activity of the electrode with 50-70% lr is attributed to not only its good electrocatalytic effect but also its large electrochemically active surface area, especially the contribution of the inner surface.