Investigation of the electrical properties, charging process, and passivation of RuO2-Ta2O5 oxide films (original) (raw)

2006, Journal of Electroanalytical Chemistry

Freshly prepared RuO 2 -Ta 2 O 5 thin films containing between 10 and 80 atom% Ru have been examined and characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and morphological analysis (SEM -scanning electron microscopy/ EDS -energy dispersive X-ray spectroscopy). Investigation of the electrical properties, charging process, and passivation of the electrode containing RuO 2 -Ta 2 O 5 thin films was conducted as a function of electrode composition in a 0.5 mol dm À3 H 2 SO 4 solution. For potential values in the double layer region (0.2-1.0 V vs. RHE), the impedance profile observed at low frequency domain was attributed mainly to the capacitive behavior of the oxide/solution interface. As for the high frequency domain, the impedance profile gave evidence that the kinetic process is limited by supporting electrolyte/water diffusion inside the pores of the difficult-to-access oxide regions and/or the Ti/ oxide interface. The electrode passivation mechanism toward OER (oxygen evolution reaction -1.5 V vs. RHE) was also investigated during long-term electrolysis (j = 750 mA cm À2 and T = 80°C) by means of EIS at pre-established times. The SEM-EDS data give evidence of the increase in the TiO x interlayer. Moreover, the EIS data furnished complementary insight that helped our proposition of the deactivation mechanism.

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