Structural and Chemical Evolution of the SOFC Anode La_0.30Sr_0.70Fe_0.70Cr_0.30O_3−δ upon Reduction and Oxidation: An in Situ Neutron Diffraction Study

Abstract

Although some perovskite oxides have been shown to be stable solid oxide fuel cell (SOFC) anodes, the actual crystal structure of these materials under operating conditions is largely unknown. In this paper, the structural evolution of the SOFC anode La 0.30 Sr 0.70 Fe 0.70 Cr 0.30 O 3-δ was studied at 800 and 900 °C (similar to SOFC operating temperatures) in progressively reducing and oxidizing environments. The perovskite was shown to be stable down to a pO 2 of 10 -20 atm at 800 °C and a pO 2 of 10 -18 atm at 900 °C, at which point a spinel phase formed. Further reduction led to the formation of Fe metal. The phase separation of La 0.30 Sr 0.70 Fe 0.70 Cr 0.30 O 3-δ was also shown to be completely reversible with an increase in the partial oxygen pressure and reoxidation of the sample.

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La0.6Sr0.4FeO3−δ Materials by Hydrogen Reduction

“…Of special importance in electrocatalysis is the precipitation, segregation, and exsolution of iron from iron-rich perovskite materials, occurring under sufficiently reducing conditions. 3−6 In most cases, reversible antisegregation is again observed upon reoxidation, e.g., as outlined in ref (3). For LSF, this iron metal segregation, already induced by mild reductive cathodic polarization in a H 2 /H 2 O mixture, has been shown to lead to strongly enhanced electrochemical water-splitting kinetics.…”

Decreasing the Polarization Resistance of (La,Sr)CrO3−δ Solid Oxide Fuel Cell Anodes by Combined Fe and Ru Substitution

“…SrCrO 4 has been observed before as a minority phase in (La,Sr)CrO 3−δ -based solid solutions and is likely forming here owing to the proximity of these samples to the solubility limit for Cr in the LSCrFeRu perovskite, found in prior structural studies on La 1−x Sr x Cr 1−xFe x O 3−δ to lie near x = 0.67. 29,30 These studies also found that SrCrO 4 disappears upon heat treatment in hydrogen, so this secondary phase is unlikely to impact how LSCrFeRu performs as a SOFC anode in reducing fuel conditions. 29 3.2.…”

Composite manganate oxygen electrode enhanced with iron oxide nanocatalyst for high temperature steam electrolysis in a proton-conducting solid oxide electrolyzer

“…What is more, iron oxide (Fe 2 O 3 ) plays an important role in the photoanode of cells for photoelectrochemical water oxidation because of balancing the needs for photon absorption and charge separation against the demands of stability particularly for catalytic ability [28]. In addition, it is reported that iron doped into electrode material is able to improve electrode performance as well as catalytic activity in solid oxide fuel cells and electrolyzers [29,30]. So, Fe 2 O 3 -loaded LSM composite oxygen electrode is expected to effectively improve the performances in a proton-conducting solid oxide electrolyzer for high temperature steam electrolysis.…”