Oxygen partial pressure dependence of in situ X-ray absorption spectroscopy at the Co and Fe K edges for (La0.6Sr0.4)(Co0.2Fe0.8)O3−δ

Itoh, Takanori; Shirasaki, Saori; Ofuchi, Hironori; Hirayama, Sayaka; Honma, Tetsuo; Nakayama, Masanobu

doi:10.1016/j.ssc.2011.11.031

Cited by 17 publications

(13 citation statements)

References 19 publications

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“…A similar energy shift has been reported by Harvey et al for BSCF catalysts, and it is consistent with the reduction of Co(III) to Co(II) . Other authors reported an energy shift of ∼1 eV for LSCF systems with different composition (Co = 0.8, Fe = 0.2) and attributed this effect to a decrease of the average Co valence toward Co(III) or lower average valence. − It is well acknowledged that Co(IV) is formed in the lanthanum cobaltite (LCO) when La 3+ is replaced with Sr 2+ , inducing an increase of the average Co oxidation state and a straightening of the octahedral cage. ,,, Indeed, the presence of Co(IV) has been reported by several authors also for LSCF and BSCF at different Co/Fe ratios. − , …”

Section: Resultssupporting

confidence: 83%

“…9,10,31,38 Indeed, the presence of Co(IV) has been reported by several authors also for LSCF and BSCF at different Co/Fe ratios. [34][35][36][37]28 Due to the large edge shift shown in Figure 6 (∼4 eV), it can be concluded that Co(III) and Co(IV) present in the structure are mostly reduced to Co(II), while evidence of the mere reduction of Co(IV) to Co(III) is not recognizable. Remarkably, only a negligible energy shift (<0.5 eV), measured in the same temperature range of unpromoted catalysts (see Figure 6), is observed for the sample LSCF08-Ni.…”

Section: Fabrication Of Symmetric Cells and Ac Impedancementioning

confidence: 99%

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The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

et al. 2018

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We investigated the effect of nickel doping on the electronic structure and performance of nanostructured La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ prepared by the one-pot sol–gel method. The commercial undoped La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF0.8) was used as reference. Moreover, for comparison, Ni (3 mol %) was deposited by wetness impregnation over the La0.6Sr0.4Co0.2Fe0.8O3−δ. We show by in situ X-ray absorption spectroscopy at 900 °C under air flow that nickel enters the B perovskite site of the material and favors the stabilization of the cobalt oxidation state, as evidenced by the delay in the decrease of the average Co valence with respect to undoped samples. Our results are further supported by in situ X-ray Raman spectroscopy (XRS) that allowed us to monitor the temperature evolution of the O K-edge. XRS evidences that nickel-doped LSCF shows unmodified O2p-TM3d density of states, which proves that the Co oxidation state is preserved. Electrochemical impedance spectroscopy measurements were carried out over half-cell systems consisting of LSCF-based materials deposited onto a Ce0.8Gd0.2O2−δ electrolyte. The improvement of the electrochemical performances of the Ni-doped La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ sample with respect to a reference Ni-impregnated LSCF is attributed to the stabilization of the TM-O6 structural units, which were recently proposed as the functional units for oxygen reduction.

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Section: Resultssupporting

confidence: 83%

Section: Fabrication Of Symmetric Cells and Ac Impedancementioning

confidence: 99%

The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

et al. 2018

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“…In other words, the oxygen vacancies are preferred close to the cobalt ions but not close to the iron ions. Similar results were also obtained by Itoh et al [31,32] and Mueller et al [33]. In addition, independent and detailed theoretical investigations on the oxygen vacancy formation in cubic BSCF which were performed oxygen pathways in orthorhombic BSCF and the results are shown in Figure 6.…”

Section: Resultssupporting

confidence: 83%

Detailed insights into the structural properties and oxygen-pathways in orthorhombic Ba0.5Sr0.5Co0.8Fe0.2O3–δ by electronic-structure theory

et al. 2012

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A number of structural properties of orthorhombic Ba0.5Sr0.5Co0.8Fe0.2O3- (BSCF) have been investigated by means of quantum-chemical calculations based on densityfunctional theory (DFT) and compared with experimental results. The role of the cation arrangements and the location of the oxygen vacancies within the orthorhombic structure have been evaluated and explained by means of bond-analytical techniques.Moreover, a detailed investigation of all oxygen pathways within orthorhombic BSCF

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“…This relationship has been extensively studied for a number of transition metal perovskite oxides. 35,[54][55][56][57][58][59] The normalized XANES spectra and pre-edge peaks of the Co K-edge are shown in Fig. 10(a) and (b), respectively.…”

Section: X-ray Absorption Spectramentioning

confidence: 99%

Correlation between structure and mixed ionic–electronic conduction mechanism for (La_1−xSr_x)CoO_3−δ using synchrotron X-ray analysis and first principles calculations

et al. 2015

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The mechanism of mixed ionic-electronic conduction (MIEC) for (La 1Àx Sr x )CoO 3Àd (LSC) (x ¼ 0.00-0.50) was investigated by experimental as well as theoretical studies which included Rietveld refinements, maximum entropy method (MEM) analysis, X-ray absorption spectroscopy, and first principles calculations (FPCs). The correlations among MIEC, structural parameters, i.e., the bond length, the bond angle, electron density, and the spin configuration, were discussed from the practical results. Moreover, these correlations were verified by FPC, and interpreted by the band structure and the total energy of LSC. The electronic conductivity was affected by the Co-O-Co bond angle, electron densities, and the spin state. In particular, the spin transition from the low to high spin state was accompanied by the cross-over from semiconductor to metallic at x ¼ 0.15. Concerning the oxide ion diffusion, LSC has large anisotropic atomic displacement parameters of the oxide ion sites, in the vertical direction of the Co-O bond, which associate with the high oxide ion diffusion. The total energy of LSC during the migration of the oxide ion was also calculated with varying Sr content, lattice parameters, and symmetries by using FPC. Consequently, the symmetry of LSC is more effective to reduce the activation energy of oxide ion diffusion than Sr content and lattice parameters.

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Oxygen partial pressure dependence of in situ X-ray absorption spectroscopy at the Co and Fe K edges for (La0.6Sr0.4)(Co0.2Fe0.8)O3−δ

Cited by 17 publications

References 19 publications

The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

Detailed insights into the structural properties and oxygen-pathways in orthorhombic Ba0.5Sr0.5Co0.8Fe0.2O3–δ by electronic-structure theory

Correlation between structure and mixed ionic–electronic conduction mechanism for (La_1−xSr_x)CoO_3−δ using synchrotron X-ray analysis and first principles calculations

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Oxygen partial pressure dependence of in situ X-ray absorption spectroscopy at the Co and Fe K edges for (La0.6Sr0.4)(Co0.2Fe0.8)O3−δ

Cited by 17 publications

References 19 publications

The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

Detailed insights into the structural properties and oxygen-pathways in orthorhombic Ba0.5Sr0.5Co0.8Fe0.2O3–δ by electronic-structure theory

Correlation between structure and mixed ionic–electronic conduction mechanism for (La1−xSrx)CoO3−δ using synchrotron X-ray analysis and first principles calculations

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Product

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Correlation between structure and mixed ionic–electronic conduction mechanism for (La_1−xSr_x)CoO_3−δ using synchrotron X-ray analysis and first principles calculations