Mechanism of La0.6Sr0.4Co0.2Fe0.8O3 cathode degradation

Oh, Dongjo; Gostovic, Danijel; Wachsman, Eric D.

doi:10.1557/jmr.2012.222

Cited by 216 publications

(181 citation statements)

References 35 publications

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“…Hence, a detailed picture of surface defect chemistry remains largely unresolved. Furthermore, while we here focus on LaMnO 3 as a representative of the LSM system, other TM-based mixed ionicelectronic conducting oxides [e.g., (La 1−x Sr x )CoO 3 [28,29] and (La 1−x Sr x )(Co 1−y Fe y )O 3 [30,31]] are being explored for solid oxide fuel cells, and similar uncertainty to that in LSM exists about their surface defect chemistry. The present studies focus on general trends associated with the surface energetics and TM properties, particularly for TM-based mixed ionic-electronic conducting perovskites with an e g orbital degeneracy, which exhibit energetically facile redox capability, and are commonly used in solid oxide fuel cell cathode applications.…”

Section: Introductionmentioning

confidence: 99%

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
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In this paper, we perform a comparative study based on ab initio modeling for perovskite ABO 3 (001) surfaces and surface defect energetics in order to understand the influence of polarity and redox active Mn in the LaMnO 3 system. We consider LaMnO 3 , LaAlO 3 , SrTiO 3 , and briefly LaFeO 3 systems for comparison, which illustrate the interplay between properties of polar surfaces and the varying d-electron shell of transition metals. We are motivated by the need to understand the surfaces of mixed electronic and ionic conductors typically used in solid oxide fuel cell cathodes and other ion conducting technologies, which are represented here by the LaMnO 3 system. We focus on the influence of the metal character and surface polarity on the surface and surface defect chemistry in these selected systems. We demonstrate that the facile redox of the TM (3d 4 ) in LaMnO 3 with partial e g orbital occupation (or specifically e g occupancy close to 1) allows the polar surfaces to be compensated by changes in charge density over relatively short length scales (3 to 4 unit cells or ∼1.5 nm) near the surface as compared to LaAlO 3 . In contrast to LaAlO 3 , this low-energy and short-range screening mechanism leads to low surface energies without any additional reconstruction, rapidly converging surface properties with film thickness (by ∼8 unit cells), bulklike defect chemistry more than ∼1.5 nm from the surface, and surface defect energetics that are primarily governed by the local charge doping or the created electric field near the polar surfaces. We show that LaMnO 3 exhibits very different surface properties from LaAlO 3 and SrTiO 3 , thereby demonstrating that these properties are due to the presence of the redox active transition metal with partial e g orbital occupation and a polar surface, respectively. These understandings can help guide qualitative analysis, computational study, and design of surfaces of mixed electronic and ionic conductors.

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Section: Introductionmentioning

confidence: 99%

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
View full text Add to dashboard Cite

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“…Moreover, the correlation between their redox behavior under electrochemical operating conditions is still unclear. Many studies have been devoted to investigating LSCF degradation and several causes have been reported, among them: i) mutual cations diffusion between interfaces with consequent atoms depletion and phase separation, [11][12][13][14][15][16] ii) LSCF grain coarsening, 17 iii) reactivity with YSZ-based electrolytes, even with ceria-based barrier layer, 18 iv) impurity contamination, namely Cr from metal interconnects and B from sealing when the cell is inside a stack.…”

mentioning

confidence: 99%

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δversus Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ

Giuliano

Carpanese

Clematis

et al. 2017

J. Electrochem. Soc.

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The two half-cell systems were compared to evaluate the influence of infiltration, overpotential and ageing on their performance and stability. Structure, microstructure and chemical composition were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray spectroscopy (EDX), whereas redox behavior was evaluated through temperature programmed reduction (TPR) and thermal gravimetric analysis (TGA) in combination with electrochemical impedance spectroscopy (EIS), which was also used to test the electrochemical performance. A decrease of polarization resistance for both infiltrated electrodes, compared to the reference ones, was highlighted at open circuit voltage (OCV), although the BSCF-based cathode was more benefitted more from infiltration than the LSCF-based one. Moreover, the application of cathodic overpotentials (−0.1 to −0.3 V) resulted in opposite effects on the LSCF-and BSCF-based cathodes, highlighting a different response of the oxygen vacancies to the applied voltage for the two perovskite compositions. The positive effect of the LSM layer was further confirmed by the observed improvement in long-term stability of both infiltrated perovskite-type systems. 1 They exhibit mixed ionic and electronic conductivity, with excellent charge and mass transfer properties 2 and high oxygen exchange surface coefficients. 3 Their excellent activity for oxygen reduction has been proved widely. [4][5][6][7][8][9][10] Although the structure and electrochemical processes of LSCF and BSCF are quite different, both of them have long-term stability and redox behavior issues to be clarified, in order to be used as cathode materials in commercial devices. Indeed, when used as cathodes in intermediate-temperatures solid oxide fuel cells (IT-SOFCs), they suffer from chemical and structural instability, which causes degradation during operation time. Moreover, the correlation between their redox behavior under electrochemical operating conditions is still unclear. Many studies have been devoted to investigating LSCF degradation and several causes have been reported, among them: i) mutual cations diffusion between interfaces with consequent atoms depletion and phase separation, [11][12][13][14][15][16] ii) LSCF grain coarsening, 17 iii) reactivity with YSZ-based electrolytes, even with ceria-based barrier layer, 18 iv) impurity contamination, namely Cr from metal interconnects and B from sealing when the cell is inside a stack.19-21 Some recent work performed on an LSCF/CGO (Ce 0.9 Gd 0.1 O 2-δ ) composite cathode on a YSZ electrolyte with a CGO barrier layer 11 affirms that Sr depletion, phase separation and cations inter-diffusion occur mainly during the fabrication process, with negligible contributions during long-term * Electrochemical Society Member.e Present Address: R&D Manufacturing Support Dept., Ansaldo Energia, Via Nicola Lorenzi 8, I-16152 Genoa. z E-mail: carpanese@unige.it operation (973 K). On the other hand, some previous works conversely found that LS...

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“…The large Sr 2+ is under a compressive strain/stress state in the bulk, which can be relaxed when it moves to the surface, resulting in the migration and formation of SrO species on the surface of related perovskite oxides. [47][48][49][50] However, the present study shows that in the case of open circuit operation conditions in the presence of borosilicate glass, LaBO 3 rather than strontium borate is formed on the LSM grain surface, as shown by the XPS analysis (Figs. 4 and 10), consistent with previous studies.…”

Section: Nanosims Icp-oes and Xps-mentioning

confidence: 46%

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

Chen

Liu

Guagliardo

et al. 2015

J. Electrochem. Soc.

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Borosilicate glass and glass-ceramics are the most common sealant materials for planar solid oxide fuel cells (SOFCs). This study focuses on the fundamentals of deposition and poisoning of volatile boron species from the borosilicate glass on the electrocatalytic activity and microstructure of La 0.8 Sr 0.2 MnO 3 (LSM) cathodes under accelerated SOFC operation conditions, using EIS, SEM, FIB-SEM, HRTEM, NanoSIMS, XPS and ICP-OES. The presence of boron species poisons and deteriorates the electrochemical activity and stability for the O 2 reduction reaction on the LSM cathodes. Boron deposition occurs randomly on the LSM electrode surface under open circuit but is driven to the electrode/electrolyte interface region under cathodic polarization conditions, resulting in the formation of LaBO 3 and Mn 2 O 3 and the disintegration of the LSM perovskite structure. The preferential boron deposition at the interface is most likely due to the increased activity of the highly energetic lanthanum at LSM lattice sites at the three phase boundary region under cathodic polarization conditions, accelerating the reaction rate between the gaseous boron species and energetic La. This study provides a fundamental insight into the boron deposition and its interaction with SOFC cathodes. Solid oxide fuel cells (SOFCs) are an energy conversion device to directly transfer the chemical energy of fuels to electrical energy, and are the most efficient and least polluting energy conversion technology among various kinds of fuel cells. One critical issue of the development of reliable and durable SOFCs is the gradual degradation of activity at the cathode side during long-term operation, due to the attack by volatile impurities such as chromium from the Fe-Cr interconnect, sulfur from the air stream and boron from borosilicate-based glass sealants. 1-3Borosilicate glass and glass-ceramic materials are the most common sealants to seal the edge of planar SOFCs to hermetically separate fuels supplied to the anode and air to the cathode. [4][5][6][7][8][9] The sealing and thermomechanical properties and the compatibility and interface between glass-ceramic sealant materials, metallic interconnect and electrolyte have been extensively studied. 8,[10][11][12][13][14] However, under the SOFC operation condition boron species from the borosilicate glass are highly volatile to form BO 2 under dry conditions and B 3 H 3 O 6 under wet, reducing conditions. 2,15 Earlier studies show that volatile species from glass sealants can significantly affect the microstructure of LSM electrodes.16 Komatsu et al. 17 used glass to seal an anode-supported planar cell and found that the concentration of boron in the cathode exhaust gas trapped by a water condenser increased with the operation time during the long-term test at 800• C for 6500 h. We recently carried out a series of detailed studies on the effect of boron poisoning on electrode performance of the most common (La,Sr)MnO 3 (LSM), (La,Sr)(Co,Fe)O 3 (LSCF) and (Ba,Sr)(Co,Fe)O 3 (BSCF) cathodes, by heat-...

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Mechanism of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ cathode degradation

Abstract: Abstract

Cited by 216 publications

References 35 publications

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
View full text Add to dashboard Cite

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
View full text Add to dashboard Cite

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δversus Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

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Mechanism of La0.6Sr0.4Co0.2Fe0.8O3 cathode degradation

Abstract: Abstract

Cited by 216 publications

References 35 publications

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3andLee1, Morgan2 2015Phys. Rev. B433360View full textAdd to dashboardCite

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3andLee1, Morgan2 2015Phys. Rev. B433360View full textAdd to dashboardCite

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La0.6Sr0.4Co0.2Fe0.8O3-δversus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

A Fundamental Study of Boron Deposition and Poisoning of La0.8Sr0.2MnO3Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

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Mechanism of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ cathode degradation

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
View full text Add to dashboard Cite

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3and
Lee
¹
,
Morgan
²

2015
Phys. Rev. B
43
3
36
0
View full text Add to dashboard Cite

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δversus Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions