Crystal structure, cobalt and iron speciation and oxygen non-stoichiometry of La0.6Sr0.4Co1-yFeyO3-δ nanorods for IT-SOFC cathodes

Abstract

Single-phased La 0.6 Sr 0.4 Co 1-y Fe y O 3-d (y = 0.2, 0.5, 0.8) nanorods exhibiting the rhombohedral perovskite-type phase were synthesized by a pore-wetting technique. We studied their chemical composition, crystal and electronic structures, morphology and hyperfine properties as a function of the Co/Fe content of the samples. Our results demonstrate that Co cations exhibit a slightly lower oxidation state than Fe ones, resulting in a higher oxygen non-stoichiometry d for Co-rich samples. In addition, the values of d determined in this work for nanostructured samples are much higher than those reported in the literature for bulk materials. This can be attributed to the high degree of defects in nanomaterials and is probably one important factor in the high electrochemical performance for the oxygen reduction reaction of nanostructured La 0.6 Sr 0.4 Co 1-y Fe y O 3-d IT-SOFC cathodes, which have been reported in a previous work.

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

“… 133 Alternatively, one can use integrated descriptors and determine the energy where the integrated absorption reaches a certain fixed value. For example, Capehart et al suggested using as a descriptor of the absorption edge position an energy value corresponding to 80% of the integrated absorption spectrum area for the corresponding metal foil 134 , 135 ( Figure 6 a).…”

“…Frequently, information about the oxidation state can be easily extracted from the examination of the absorption edge position since a higher oxidation state is associated with a shift of the absorption edge toward larger energies. For example, a nearly linear relationship between the Co K-edge position and the Co oxidation state has been reported (Figure a). , Using XAS spectra for reference materials with known oxidation state, the relationship between the oxidation state and the edge position can be established and used to find the oxidation state of the new material of interest. It should be however noted that instead of a nominal oxidation state, in some cases the absorption edge position rather characterizes the so-called coordination charge, which accounts for charge redistribution due to chemical bonding. , …”

Influence of Mg doping on the structural and optical properties of manganese oxide (Mn2O3) nanoparticles

“…Early research included the examination of a few manganese oxide specimens [3][4][5] and the morphological examination of manganese oxides derived from various precursors [6][7][8]. Manganese oxide shows a variety of oxidation states (+2, +3, +4) and crystal forms, including MnO, MnO 2 , Mn 2 O 3 and Mn 3 O 4 , which contribute to their effective gas sensing capabilities [9][10].…”

Bonding State and Thermal Expansion Coefficient of Mn-Doped Ba0.5Sr0.5FeO3−δ Perovskite Oxides for IT-SOFCs

“…Mixed ionic and electronic conducting (MIEC) oxides have been considered as cathode materials because of their superior ORR activity at intermediate temperatures [ 12 , 13 , 14 ]. Many cobalt-containing MIEC oxides, such as La 0.6 Sr 0.4 CoO 3−δ , La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ , and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ , have been used as cathode materials in IT-SOFCs [ 15 , 16 , 17 ].…”