Electrochemical Characterization of La[sub 0.6]Sr[sub 0.4]Co[sub 0.2]Fe[sub 0.8]O[sub 3] Cathodes for Intermediate-Temperature SOFCs

Abstract

The electrochemical properties of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 ͑LSCF͒ have been assessed for its application as a cathode in intermediate-temperature solid oxide fuel cells. van der Pauw dc conductivity, two-electrode impedance, and three-electrode measurements were carried out to investigate the kinetics of the oxygen reduction reaction at various temperatures, oxygen partial pressures, and polarization values. A change in cathode behavior at temperatures around 600°C was observed. This is interpreted in terms of LSCF behaving as a mixed ionic electronic conductor at temperatures above around 600°C, oxygen reduction being stimulated by the formation of oxygen vacancies with increasing cathode overpotential. However, at temperatures below 600°C the contribution of mixed conductivity is low, and cathode behavior can then be interpreted in terms of the classical triple-phaseboundary model.

Degradation of (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3−δ Solid Oxide Fuel Cell Cathodes at the Nanometer Scale and below

“…The activation energy for the electrode process before and after Cr poisoning is similar, being 1.55±0.02 and 1.61±0.01 eV respectively, which is in good agreement with a previous study on similar LSCF electrodes (1.54 eV) 7 and Cr poisoned LSCF using the same approach as here (1.50 eV) 5 .…”

“…Sources of Cr species can also come from stainless steel components found in the balance-of-plant (BoP) such as heat exchangers 2 . This poisoning has been found to lead to rapid electrochemical performance degradation of the cathodes [3][4][5][6] , including (La,Sr)(Co,Fe)O3-δ (LSCF) perovskite oxides, which are considered to be a promising cathode material for ITSOFCs due to their significantly higher electrochemical activity for the O 2 reduction reaction and higher oxygen ion conductivity than the conventional (La,Sr)MnO 3 (LSM) cathode 7 .…”

Thermally and Electrochemically Induced Electrode/Electrolyte Interfaces in Solid Oxide Fuel Cells: An AFM and EIS Study

“…17,59,60 On the other hand, the negligible changes in the convex contact rings at the pre-sintered LSCF/GDC interface indicate that O 2 reduction reaction occurs predominantly in the electrode bulk away from the TPB due to its high MIEC properties. 50,61 In contrast with the substantial activation effect of the cathodic polarization on the electrochemical activities of pre-sintered LSM electrodes, the changes in R E for the O 2 reduction reaction on pre-sintered LSCF electrodes under the cathodic polarization current passage are negligible (Fig. 10).…”

Electrochemical Impedance Spectroscopy Study of the Mass Transfer in an Anode-Supported Microtubular Solid Oxide Fuel Cell

“…In particular, the author's group has developed diagnosis methods of operating status of the polymer electrolyte fuel cell (PEFC) by analyzing the variation of resistances and capacitances of equivalent circuit models of the PEFC (Konomi & Saho, 2006;Nakajima et al, 2008). For the SOFC, a number of EIS analyses have been reported (Barsoukov & Macdonald, 2005;Esquirol et al, 2004;Horita et al, 2001;Huang et al, 2007;Ishihara et al, 2000;Jiang, 2002;Leonide et al, 2010;McIntosh et al, 2003). Although many of those reports focused on the characterization of developed materials, there were very few reports (Barfod et al, 2007) that analyze each impedance of the anode and cathode in the full cell impedance of a practical cell simultaneously and separately by applying EIS under operation.…”