23 October 2002 Characterization of nonsensitized and Ru(II) sensitized sol-gel Nb2O5 electrodes by impedance spectroscopy
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Abstract
The impedance spectra of non-sensitized and Ru(II)-sensitized Nb2O5 nanoporous coatings have been measured in the dark and under solar illumination using an electroactive electrolyte. All the Nyquist plots consist of a high and a low frequency depressed semicircle. The results have been modeled and fitted by an equivalent electric circuit consisting of a resistor Rs in the series with two parallel RC circuits containing both a constant phase element (CPE). The resistor Rs describes the total resistance of the electrolyte and conducting electrodes (SnO2:F). The high frequency semicircule (f<1kHz) describes the capacitance and resistance of the semiconducting materials (grain boundaries and interfaces). The low frequency cycle (f < 1 kHz) is related to the formation of a double charge layer capacitance at the nanoparticle/electrolyte interface and a charge transfer resistance. Both values are strongly dependant of the experimental conditions, in particular of the applied potential and the state of illumination. The evolution of the electric elements is presented and discussed. It is shown in particular that the measurements in the dark cannot be directly compared to those under illumination as in teh latter all the Nb2O5-film is accessed.
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Ye Ping Guo, Ye Ping Guo, Sabine Heusing, Sabine Heusing, Michel Andre Aegerter, Michel Andre Aegerter, } "Characterization of nonsensitized and Ru(II) sensitized sol-gel Nb2O5 electrodes by impedance spectroscopy", Proc. SPIE 4804, Sol-Gel Optics VI, (23 October 2002); doi: 10.1117/12.453900; https://doi.org/10.1117/12.453900
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