Impedance and Photoadmittance of Passive Iron Electrodes in Different Solutions |
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Authors: | Klyuev A. L. Rotenberg Z. A. Batrakov V. V. |
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Affiliation: | (1) Moscow State Pedagogical University, ul. Malaya Pirogovskaya 1, Moscow, 119882, Russia;(2) Frumkin Institute of Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071, Russia |
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Abstract: | Electric characteristics of the oxide film at the surface of an anodized iron electrode in 0.5 M Na2SO4, NaNO3, and Na2MoO4 solutions are studied using the impedance and photoadmittance measurements and taking polarization curves. The impedance frequency spectra correspond to an equivalent circuit comprising two parallel (RC) chains connected in a series. The relaxation time of the high-frequency circuit approaches that of the photopotential; hence, it can be related to the impedance of the oxide film. The low-frequency component of the impedance describes the impedance of the film/solution interface. In the Na2SO4 solution, the oxide film resistance is significantly higher and the capacitance is lower than in two other solutions, which can be explained by the film thickening. The marked concurrent decrease in the resistance and increase in the capacitance of the film/solution interface at 1.2 V in all solutions is caused by oxygen adsorption, which precedes oxygen evolution. |
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Keywords: | impedance photoadmittance passive iron electrode |
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