Long-term stability of the oxygen exchange properties of (La,Sr)1−z(Co,Fe)O3−δ in dry and wet atmospheres

Bucher, Edith; Sitte, Werner

doi:10.1016/j.ssi.2010.01.006

Cited by 112 publications

(79 citation statements)

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“…A recent computational study showed that transition metal cations are responsible for the electrocatalytic activity for oxygen reduction [35], suggesting that a high surface concentration of transition metal cations could facilitate surface processes. XPS and Auger electron spectroscopy studies carried out on perovskites, however, revealed that the surface concentration of the transition metal cations in the cation stoichiometric perovskites is either the same as in the volume of crystallites or lower [36][37][38][39][40][41]. It is not clear whether the presence of a second phase (cerium oxide) would change the surface concentration of transition metal cations or not.…”

Section: Introductionmentioning

confidence: 98%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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Keywords:X-ray photoelectron spectroscopy (XPS) Surface composition Composites with perovskite and fluorite structures Oxidation state of cerium cations Binding energy a b s t r a c t X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO 2 -based solid solutions and in the two phase (100 − x)La 0.6 Sr 0.4 CoO 3 -xCeO 2 (LSCCx) and (100 − x)La 0.8 Sr 0.2 MnO 3 -xCeO 2 (LSMCx) composites. The well-resolved Ce 3d 5/2 and Ce 3d 3/2 spin-orbit components were determined to study the Ce 4+ to Ce 3+ electronic transition at the surface. The surface of the LSCCx and LSMCx (x = 8-40 mol%) composites is depleted in cerium. Both Ce 4+ and Ce 3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO 2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCCx (x = 8-40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La 0.6 Sr 0.4 CoO 3 , CeO 2 -based solid solutions, LSCC57, and LSMCx (x = 10-57) composites. In contrast, the surface of the LSCCx (x = 10-37) composites is slightly depleted in strontium cations. The O 1s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO 2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce 2 (CO 3 ) 3 -based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites.

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Section: Introductionmentioning

confidence: 98%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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“…19 Adversely La 1Àx Sr x Co 1Ày Fe y O 3Àd based cathodes have been found to suffer from substantial longterm degradation, [20][21][22][23] at their operating temperatures. The effect is frequently associated with Sr enrichment of the surface leading to suppressed oxygen surface exchange kinetics due to the insulating nature of SrO (Sr(OH) 2 and SrCO 3 ) species.…”

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The synergistic effect of cobalt oxide and Gd-CeO₂ dual infiltration in LSCF/CGO cathodes

et al. 2018

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composite cathodes were nano-engineered via "dual" inkjet printing infiltration of nitrate salt solutions in a single step procedure. After calcination in air at 700 C the cathodes were decorated with Ce 0.9 Gd 0.1 O 1.9 and Co x O y nanoparticles ($20 nm in size). The effects of the as-created nano-decoration on the electrochemical activity and the performance stability in the intermediate temperature range (500-700 C) were investigated. The nano-engineered microstructure was found to extend the active three-phase boundary and to promote adsorption-dissociation-surface exchange reactions. Electrochemical impedance tests conducted on symmetric cells showed a reduction in the polarisation resistance of between 1.5 and 7.0 times depending on temperature (500-700 C). High-resolution X-ray photoelectron spectroscopy and in situ high temperature Raman spectroscopy were used to study aging and thermal cycling effects on the cathodes' surface chemistry.Aging tests of the infiltrated electrodes up to 100 hours in air revealed an enhanced stability of the decorated electrodes ascribed to the suppression of SrO surface segregation. This work demonstrated that the sequence of infiltration of both inks introduces noticeable differences in the oxygen reduction reaction.

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“…As reported by Ding et al [9] the combined effects of reduced surface stress and smaller surface charge results in SrO-terminated surfaces having lower energy than LaO-terminated surfaces thus promoting Sr segregation. The enrichment of Sr at the cathode surface leads to an increase in the cathode polarization losses through deactivation of ORR sites and decrease in surface activity [10]. Lowering the operational temperature is a straightforward way to alleviate such stability problem and to prolong the lifetime of the cell.…”

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confidence: 99%

Performance optimization of LSCF/Gd:CeO2 composite cathodes via single-step inkjet printing infiltration

et al. 2017

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Long-term stability of the oxygen exchange properties of (La,Sr)1−z(Co,Fe)O3−δ in dry and wet atmospheres

Cited by 112 publications

References 20 publications

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

The synergistic effect of cobalt oxide and Gd-CeO₂ dual infiltration in LSCF/CGO cathodes

Performance optimization of LSCF/Gd:CeO2 composite cathodes via single-step inkjet printing infiltration

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Long-term stability of the oxygen exchange properties of (La,Sr)1−z(Co,Fe)O3−δ in dry and wet atmospheres

Cited by 112 publications

References 20 publications

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

The synergistic effect of cobalt oxide and Gd-CeO2 dual infiltration in LSCF/CGO cathodes

Performance optimization of LSCF/Gd:CeO2 composite cathodes via single-step inkjet printing infiltration

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The synergistic effect of cobalt oxide and Gd-CeO₂ dual infiltration in LSCF/CGO cathodes