Cobalt–iron red–ox behavior in nanostructured La0.4Sr0.6Co0.8Fe0.2O3− cathodes

Soldati, Analía Leticia; Baqué, Laura; Napolitano, Federico; Serquis, A.

doi:10.1016/j.jssc.2012.10.019

Cited by 10 publications

(10 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

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

et al. 2018

View full text Add to dashboard Cite

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.

show abstract

Section: Resultssupporting

confidence: 83%

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

et al. 2018

View full text Add to dashboard Cite

show abstract

“…LSCF-975 requires an overpotential of 440 mV to achieve 10 mA/cm 2 which is comparable to or better than several reported perovskite electrocatalysts (Table S2). ,,− In comparison, LSCF-750 and LSCF-1200 require 470 and 540 mV, respectively. The Tafel equation (η = b log ( j ) + a , where η is the overpotential, j is the current density, and b is the tafel slope) is employed to derive the Tafel plots from LSV polarization curves (Figure b), where Tafel slope in the Faradaic region indicates the ease of OER kinetics on the catalyst surface.…”

Section: Resultsmentioning

confidence: 99%

Maneuvering the Physical Properties and Spin States To Enhance the Activity of La–Sr–Co–Fe–O Perovskite Oxide Nanoparticles in Electrochemical Water Oxidation

Majee

Chakraborty

Salunke

et al. 2018

ACS Appl. Energy Mater.

View full text Add to dashboard Cite

Perovskite oxides have attracted considerable attention as durable electrocatalysts for metal–air batteries and fuel cells due to their precedence in oxygen electrocatalysis in spite of the complexities involved with their crystal structure, spin states, and physical properties. Here we report optimization of the activity of a model perovskite system La1–x Sr x Co1–y Fe y O3−δ (LSCF; x = 0.301, y = 0.298, and δ = 0.05–0.11) toward electrochemical water oxidation (OER) by altering the calcination temperature of the nonaqueous sol–gel synthesized nanoparticles (NPs). Our results show that improved OER activity is the result of a synergism between its morphology, surface area, electrical conductivity, and spin state of the active transition metal site. With an eg orbital occupancy of 1.26, the interconnected ∼90 nm LSCF NPs prepared at 975 °C (LSCF-975) outperforms the other distinguishable LSCF morphologies, requiring 440 mV overpotential to achieve 10 mA/cm2, a performance comparable to the best-performing perovskite oxide electrocatalysts. While the interconnected NP morphology increases the propensity of electronic conduction across crystalline grain boundaries, the morphology-tuned high spin Co3+ ions increases the probability of binding reaction intermediates at the available surface sites. Density functional theory based work function modeling further demonstrates that LSCF-975 is the most favorable OER catalyst among others in terms of a moderate work function and Fermi energy level facilitating the adsorption and desorption of reaction intermediates.

show abstract

“…No Raman peaks are expected for such cubic symmetry and thus the Raman spectroscopy is very efficient to detect any structural distortion [13]. The symmetry of Ln 2 NiO 4+δ is more or less distorted either tetragonal (P42/ncm), or orthorhombic Bmab or Fmmm, depending on the lanthanide elements, the oxygen stoichiometry δ and temperature [14][15][16][17][18][19][20][21]. Phase coexistence is also often reported in polycrystalline materials.…”

Section: Introductionmentioning

confidence: 99%

“…Phase coexistence is also often reported in polycrystalline materials. As for most of perovskites, the structural phase transitions are observed with the temperature increase, for example in the case of NNO with an oxygen excess, the transition from the orthorhombic symmetry (Fmmm) to the tetragonal (I4/mmm) one is detected between 477/550°C and 600/627°C depending on authors [14][15][16][17][18][19][20][21], actually depending on the oxygen partial pressure explored during the thermal treatment. This should be stressed, the black color of a material requires special procedure for optical studies in order to avoid any local heating and associated structural changes (oxidation/stoichiometry modification) [22,23].…”

Section: Introductionmentioning

confidence: 99%

Protonation and structural/chemical stability of Ln2NiO4+ ceramics vs. H2O/CO2: High temperature/water pressure ageing tests

Upasen

Batocchi

Mauvy

et al. 2015

Journal of Alloys and Compounds

View full text Add to dashboard Cite

Mixed ionic-electronic conductors (MIEC) such as rare-earth nickelates with a general formula Ln 2 NiO 4+δ (Ln=La, Pr, Nd) appear as potential cathodes for energy production and storage systems: fuel cells, Highlights High temperature/water pressure autoclave is used to study the reaction/corrosion at SOFC/HTSE electrode. High stability of Pr 2 NiO 4+δ (PNO) and Nd 2 NiO 4+ δ (NNO) dense ceramics vs. water pressure is demonstrated. Protonated rare-earth nickelates retain the perovskite-type structure and their H-content is determined. Very low laser illumination power is required to avoid RE nickelate phase transition. Nickelates show increasing stability from La to Pr/ Nd vs. CO 2-rich high temperature water vapour

show abstract

Cobalt–iron red–ox behavior in nanostructured La0.4Sr0.6Co0.8Fe0.2O3− cathodes

Cited by 10 publications

References 36 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

Maneuvering the Physical Properties and Spin States To Enhance the Activity of La–Sr–Co–Fe–O Perovskite Oxide Nanoparticles in Electrochemical Water Oxidation

Protonation and structural/chemical stability of Ln2NiO4+ ceramics vs. H2O/CO2: High temperature/water pressure ageing tests

Contact Info

Product

Resources

About