B-site substituted lanthanum strontium ferrites as electrode materials for electrochemical applications

Abstract

Abstract:For electrochemical systems such as solid oxide fuel cells (SOFCs) or solid oxide electrolyzer cells (SOECs), perovskites are widely used as cathode material for the reduction of molecular oxygen. At present, strontium-substituted lanthanum manganite, La 1-x Sr x MnO 3-δ (LSM), is used as standard SOFC cathode material for operation at high temperatures, whereas strontium-substituted lanthanum ferrite (LSF) is alternatively explored for medium-temperature SOFCs. Moreover, LSF is considered to be a potential candidate for oxygen separation membranes as the material reported interesting electrical properties. The design of new perovskite-type La transition-metal oxides is of significant technological importance in order to reduce the operating temperature to 600-800 °C and thus to reduce the SOFC system cost.For investigations on a new material class, (La 1-x Sr x ) y Fe 1-z (Ni,Cu) z O 3-δ was synthesized by a spray-pyrolysis process and modified on the A-site in both stoichiometric and nonstoichiometric configurations and on the B-site by substituting Fe with Ni and Cu.

Characterization and Stack Testing of Solid Oxide Fuel Cells with Cathodes Prepared by Infiltration

“…5. The observed trends in conductivity were in a good qualitative agreement with previously reported results for pure dense LSF, 24,26,27 although the measured conductivity values were, depending on the sintering temperature, between 200 and 600 times lower. Temperature dependence for the total conductivity of (La 0.6 Sr 0.4 ) 0.95 FeO 3 -YSZ electrodes was similar to the data reported for pure (La 0.8 Sr 0.2 ) 0.95 FeO 3 by Vogt et al, 24 although in their paper, the conductivity maximum for (La 0.8 Sr 0.2 ) 0.95 FeO 3 was observed at lower temperatures.…”

“…No additional phases could be detected within the electrode, in good agreement with previous reports by other groups. 14,24,25,[30][31][32] Single-cell testing.-The electrochemical performance of a cell with a 24-wt% LSF-YSZ cathode prepared by infiltration is shown in Fig. 4.…”

“…LSF-SZ is an excellent model system, as LSF is a mixed ionic and electronic conductor (MIEC) with sufficient activity toward the oxygen reduction reaction. [19][20][21][22][23][24][25][26][27][28][29] Furthermore, the formation of low-conductivity secondary phases (which complicate electrochemical analysis) has not been observed for the LSF-YSZ system even at temperatures of 1100…”

“…• C. 14,24,25,[30][31][32] In addition to electrochemical results from single cell tests and short-term stack tests, a thorough physical characterization of infiltrated electrodes is presented. In particular, the in-plane conductivity, the BET surface area as well as the pore-size distribution of the cathode are reported.…”

Influence of A‐Site Variation and B‐Site Substitution on the Physical Properties of (La,Sr)FeO3Based Perovskites

“…Previous investigations [11] showed that the total conductivity of LSF depends on the composition and stoichiometry. At temperatures around 800°C, it ranges between 50 and 120 S cm -1 and is thus lower than LSM, which reaches up to 200 S cm -1 at 950°C.…”