Performance stability and degradation mechanism of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ cathodes under solid oxide fuel cells operation conditions

Liu, Yihui; Chen, Kongfa; Zhao, Ling; Chi, Bo; Pu, Jian; Li, Jian

doi:10.1016/j.ijhydene.2014.03.077

Cited by 100 publications

(42 citation statements)

References 31 publications

(33 reference statements)

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“…For example, deactivation in LSCF cathodes has frequently been associated with segregation of Sr cations. [27][28][29] The high degree of compositional control provided by ALD of Fe 2 O 3 may allow titration of the Sr in the form of SrFeO 3 and re-activation of the electrode. 30,31 Finally, we suggest that ALD has great promise for producing electrodes with complex and potentially promising surface structures.…”

Section: Discussionmentioning

confidence: 99%

Modification of LSF-YSZ Composite Cathodes by Atomic Layer Deposition

Rahmanipour

Cheng

Onn

et al. 2017

J. Electrochem. Soc.

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Composite, Solid-Oxide-Fuel-Cell (SOFC) electrodes of La 0.8 Sr 0.2 FeO 3 (LSF) and yttria-stabilized zirconia (YSZ) were prepared by infiltration methods and then modified by Atomic Layer Deposition (ALD) of ZrO 2 , La 2 O 3 , Fe 2 O 3 , or La 2 O 3 -Fe 2 O 3 codeposited films of different thicknesses to determine the effect of surface composition on cathode performance. Film growth rates for ALD performed using vacuum procedures at 573 K for Fe 2 O 3 and 523 K for ZrO 2 and La 2 O 3 were determined to be 0.024 nm ZrO 2 /cycle, 0.019 nm La 2 O 3 /cycle, and 0.018 nm Fe 2 O 3 /cycle. For ZrO 2 and Fe 2 O 3 , impedance spectra on symmetric cells at 873 K indicated that polarization resistances increased with coverage in a manner suggesting simple blocking of O 2 adsorption sites. With La 2 O 3 , the polarization resistance decreased with small numbers of ALD cycles before again increasing at higher coverages. When La 2 O 3 and Fe 2 O 3 were co-deposited, the polarization resistances remained low at high film coverages, implying that O 2 adsorption sites were formed on the co-deposited films. The implications of these results for future SOFC electrode development are discussed. Atomic Layer Deposition (ALD) is attracting an increasing level of attention as a method for modifying SOFC electrodes because the surface composition can be modified with unparalleled precision. 1-11Uniform, atomic-scale films are formed in ALD by repeated cycles in which the surface is first allowed to react with an organometallic precursor, followed by a subsequent oxidation step. Since the reaction of the precursor with the surface is performed under conditions which limit the extent of reaction to one monolayer at most, the thickness of the final oxide film can be precisely controlled by the number of cycles.In the case of SOFC cathodes, ALD has been used to improve both electrode stability and decrease impedance.1-4 For example, Gong et al. reported that degradation rates for cathodes based on La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) decreased significantly after depositing a 5-nm ZrO 2 film.3,4 While they reported a slight increase in the initial electrode impedance, the performance of the ALD-modified electrode surpassed that of the unmodified electrode after less than 100 h and exhibited a much lower impedance after 900 h of operation at 1073 K. In another example of cathodes modified by ZrO 2 ALD films, the initial impedance of composite cathodes of Sr-doped LaMnO 3 (LSM) and yttria-stabilized zirconia (YSZ) actually decreased following deposition of films as thick as 60 nm. 6 This latter study is particularly revealing because it had been previously reported that infiltration of CoO x nanoparticles could be used to decrease cathode polarization.13 Choi et al. suggested that addition of CoO x by ALD differs from infiltration because infiltration produces inhomogeneous layers that affect surface area and because the infiltration process may induce changes in the cathode morphology. 6 In principle, ALD allows catalytic materials to ...

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Section: Discussionmentioning

confidence: 99%

Modification of LSF-YSZ Composite Cathodes by Atomic Layer Deposition

Rahmanipour

Cheng

Onn

et al. 2017

J. Electrochem. Soc.

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“…As a result, less effective reaction areas and more secondary insulating phase formation suppress the overall oxygen reduction reaction activity. It has been found that partial decomposition of the perovskite usually has severely influence on the cell degradation than interface reactions during the operation [ [116][117][118][119][120][121][122][123].The improvement of cathode long-term performance is one of the most important issues for the development of IT-SOFCs.…”

Section: Electrolytementioning

confidence: 99%

Developing high performance and stable hetero-structured cathodes and fundamental understanding of oxygen reduction and reaction behavior

Zhang¹

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Developing High Performance and Stable Hetero-structured Cathodes and Fundamental Understanding of Oxygen Reduction and Reaction Behavior ByXinxin Zhang New hetero-structured La2NiO4+δ (LNO)/ (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) SOFC cathodes have been successfully fabricated by the infiltration technique for long-term stability and oxygen reduction reaction (ORR) kinetic consideration. The current comparative study of LSCF and LNO-infiltrated LSCF shows a significant reduction in polarization resistance by one order of magnitude and a 67% increase in maximum power density by using LNO-infiltrated LSCF cathodes at 750 o C in air. The electronic conductivity relaxation (ECR) results demonstrate that the remarkable improved oxygen exchange properties of LNO/LSCF hetero-structured cathodes are attributed to not only the increase of surface reaction area, but also the introduction of LNO surface and LNO-LSCF interface with rapid oxygen exchange behavior. A trace amount of Co, Sr and more oxygen defects stabilized in the LNO layer have been identified by TEM, EDXS, XPS, XRD and iodine titration experiments, giving rise to the enhancement of stability and surface catalytic activity. A low degradation rate of 0.39% at a constant current density of 250 mA•cm-2 can be still achieved for the fuel cell using LNO-infiltrated LSCF cathodes after long-term durability of about 500 h at 750 o C, accompanied by nanoparticles growth/aggregation, delamination and slight lanthanum enrichment on LNO surfaces. The benefits from the presence of the LNO nanoparticles demonstrate that LNO-infiltrated LSCF materials can act as high active surface oxygen exchange cathodes with promising fast ORR behavior and stability. To further enhance the long-term stability of infiltrated (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) cathode, two kinds of new hetero-structured cathodes, CeO2 & LNO co-infiltrated LSCF and La2-xNiO4+δ-infiltrated LSCF, have been designed. La2NiO4+δ (LNO), as an superior performance promoter, and CeO2, as a particle growth retardant due to the high melting point and good wettability, were co-infiltrated into the LSCF backbone to mitigate the delamination and growth/aggregation of in-situ formed nano-sized infiltrants. A more advantageous microstructure was confirmed in the co-infiltrated sample relative to those infiltrated with LNO alone. The original morphology was largely retained in the coinfiltrated sample after heat treatment, showing finer surface particles, better connection between the infiltrant network and the LSCF backbone. XPS and EIS results reveal that the substitution of stoichiometric La2NiO4+δ by A-site deficient La2-xNiO4+δ can effectively suppress lanthanum enrichment and enhance the stability after cathodic polarization treatment observed by measurement. The advantages of both modified hetero-structured cathodes suggest that CeO2 & La2-xNiO4+δ co-infiltrated LSCF is a promising heterostructured cathode to mitigate the LSCF electrode degradation. iv ACKNOWLEDGMENTS My deepest gratitude goes first and foremost...

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“…However, the Sr contained in SBSCO causes segregation on the surface, causing problems such as reduction of electrochemical properties and long-term performance (Liu et al, 2014;Zhao et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

SmBa1-xCaxCo2O5+d Layered Perovskite Cathodes for Intermediate Temperature-operating Solid Oxide Fuel Cells

et al. 2021

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In SmBa1-xCaxCo2O5+d (x = 0.01, 0.03, 0.1, and 0.2, SBCCO) oxide systems calcined at 1100°C for 8 h, the XRD patterns of the SBCCO single phase were maintained in the cases of SmBa0.97Ca0.03Co2O5+d (SBCCO-0.97) and SmBa0.99Ca0.01Co2O5+d (SBCCO-0.99) compositions. In SmBa0.8Ca0.2Co2O5+d (SBCCO-0.8) and SmBa0.9Ca0.1Co2O5+d (SBCCO-0.9), CaCoSmO4 existed with the pattern SBCCO. SBCCO structures were identified as orthorhombic crystal structures because they showed splitting of the X-ray diffraction (XRD) peaks at 23.4°, 47.9°, and 59.1°.Typical metallic conduction behaviors were found in all measured compositions except SBCCO-0.8, which showed a metal-insulator transition (MIT) behavior. Compared to other SmBa1-xCaxCo2O5+d compositions, SBCCO-0.8 showed the highest electrical conductivity of 460 S/cm at 500°C. In particular, SBCCO-0.9 was found to have an excellent ASR characteristic of about 0.077 Ωcm2 at 700°C. The activation energy of SBCCO-0.9 was the lowest among SBCCO oxide systems with a value of 0.77 eV.

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Performance stability and degradation mechanism of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ cathodes under solid oxide fuel cells operation conditions

Abstract: Performance stability and degradation mechanism of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathodes under solid oxide fuel cells operation conditions

Cited by 100 publications

References 31 publications

Modification of LSF-YSZ Composite Cathodes by Atomic Layer Deposition

Modification of LSF-YSZ Composite Cathodes by Atomic Layer Deposition

Developing high performance and stable hetero-structured cathodes and fundamental understanding of oxygen reduction and reaction behavior

SmBa1-xCaxCo2O5+d Layered Perovskite Cathodes for Intermediate Temperature-operating Solid Oxide Fuel Cells

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