Cyclic voltammetry characterization of a La(0.8)Sr(0.2)Co(0.2)Fe(0.8)O(3) (-) (delta) electrode interfaced to CGO/YSZ

The electrochemical characteristics of a La0.8Sr0.2Co0.2Fe0.8O3 (- delta) cathode electrode interfaced to the CGO layer of a double layer CGO/YSZ electrolyte were studied using cyclic voltammetry, at temperatures of 600 to 850 degrees C and under oxygen partial pressures ranging from 0.07 to 21 kPa. The aim was to identify the electrochemical processes taking place under cathodic polarization on the basis of differences in the features of the cyclic voltammograms with changing conditions. Depending on temperature, sweep rate and oxygen partial pressure, current peaks appeared both in the forward and backward scans. Furthermore, reversed hysteresis was observed, i.e. higher currents in the backward scan than in the forward scan, with increasing oxygen partial pressure and decreasing temperature. The observed behavior was related to the electrochemical redox of B-sites and concomitant stoichiometry change as well as to the competing reaction of electrochemical oxygen redox, taking also into account the competitive action of chemical reactions occurring in the presence of gaseous oxygen. (C) 2011 Elsevier B.V. All rights reserved

Cyclic Voltammetry of La0.78Sr0.2FeO3-d and La0.78Sr0.2Co0.2Fe0.8O3-d Electrodes Interfaced to CGO/YSZ

The electrochemical characteristics of La0.78Sr0.2FeO3-delta (L78SF) and La0.78Sr0.2Co0.2Fe0.8O3-delta (L78SCF) cathode electrodes interfaced to a double layer Ce0.8Gd0.2O2-delta (CGO)/YSZ electrolyte were studied using cyclic voltammetry, in the temperature range of 600 to 850 degrees C and under flow of 0.7% O-2 in He. The aim was to identify the electrochemical processes taking place under cathodic polarization. Current peaks were observed in the voltammograms, corresponding to potential and currents dependent on scan rate and temperature. The observed cathodic peaks can be related to reduction of the iron or/and cobalt ions but also to the competing reaction of oxygen reduction. (c) 2008 Elsevier B.V. All rights reserved

Electrochemical characterization of perovskite-based SOFC cathodes

The electrochemical performance of La0.58Sr0.4Co0.2Fe0.8O3-delta (L58SCF), La0.78Sr0.2Co0.2Fe0.8O3-delta (L78SCF) and composite La0.65Sr0.3MnO3-delta - 8 mol% Y2O3 stabilized ZrO2 (LSM-YSZ, 50:50 wt%) cathode electrodes interfaced to a double-layer electrolyte made of Ce0.8Gd0.2O2-delta (CGO) and YSZ was studied in the temperature range 600-850 degrees C using impedance spectroscopy and current-overpotential measurements. The experiments were carried out in a single chamber cell using a three electrode set-up with porous Pt films as auxiliary electrodes. The perovskite powders were synthesized using the spray-drying technique starting from nitrate precursors and were deposited on the solid electrolyte via screen-printing. Open circuit impedance measurements on as-prepared electrodes, i.e. before any polarization, and micropolarization measurements have shown that the L78SCF/CGO/YSZ electrode exhibits the lowest area specific polarization resistance R-F (R-F was approximately equal to 0.4 Omega cm(2) at 800 degrees C and P-O2 = 21 kPa) or, equivalently, the highest electrocatalytic activity according to the order: LSM/LSM-SZ/CGO/YSZ < L58SCF/CGO/YSZ < L78SCF/CGO/YSZ. Current-overpotential data taken over an extended cathodic overpotential (ohmic-drop-free) range (0 to -500 mV) also indicated the aforementioned order of electrocatalytic activity. The Nyquist plots corresponded to at least two overlapping arcs or, equivalently, to at least two rate limiting processes. The relative contribution and degree of overlap of these arcs depended on electrode material, temperature and oxygen partial pressure, the low frequency arc being in general dominant at low temperatures and low oxygen partial pressures. Open circuit impedance experiments carried out at different oxygen partial pressures P-O2 (0.01-100 kPa) revealed an exponential increase of the open-circuit area specific polarization conductance R-F(-1) with increasing P-O2

Electrochemical characterization of mixed conducting and composite SOFC cathodes

The electrochemical performance of La0.58Sr0.4Co0.2Fe0.8O3-delta (L58SCF), La0.9Sr1.1FeO4-6 (LS2F) and LSM (La0.65Sr0.3MnO3-delta)/LSM-YSZ (50 wt.% LSM-50 wt.% ZrO2 (8 mol% Y2O3)) cathode electrodes interfaced to a double layer Ce0.8Gd0.2O2-delta (CGO)/YSZ electrolyte was studied in the temperature range of 600 to 850 degrees C and under flow of 21% O-2/He mixture, using impedance spectroscopy and current density-overpotential measurements. The L58SCF cathode exhibited the highest electrocatalytic activity for oxygen reduction, according to the order: LS2F/CGO/YSZ <= LSM/LSM-YSZ/CGO/YSZ < L58SCF/CGO/YSZ. (c) 2006 Elsevier B.V. All rights reserved