AFM investigations on the influence of CO2 exposure on Ba0.5Sr0.5Co0.8Fe0.2O3–δ

Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm 0.2 Ce 0.8 O 1.9 electrolyte and sintered at 1,000°C. In the second technique, an aqueous solution of AgNO 3 was added to a previously sintered BSCF cathode, which was then sintered again at 800°C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm 0.2 Ce 0.8 O 1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600°C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samariadoped ceria as an electrolyte and Ni-Gd 0.2 Ce 0.8 O 1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.

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“…BSCF reveals some degree of instability. It reacts with CO 2 present in oxidant gaseous mixtures, forming oxides and carbonates [9] as follows: …”

Section: Introductionmentioning

confidence: 99%

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Mosiałek

Dudek

Michna

et al. 2014

J Solid State Electrochem

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“…The cubic structure of BSCF tends to collapse during the long-term operation at a temperature below 900 o C [21][22][23] and exposure to CO 2 leads to the formation of (Ba,Sr)CO 3 carbonates, deteriorating the electrochemical activity of the BSCF cathodes. [24][25][26] The presence of volatile Cr species from chromia-forming metallic interconnects also deteriorates the electrode microstructure and electrocatalytic activity. 27,28 In the case of BSCF hollow fibers for oxygen separation, the use of sulfur-containing polymer in the BSCF slurry can result in formation of barium sulfate in the fibers.…”

Section: Introductionmentioning

confidence: 99%

Effect of Volatile Boron Species on the Electrocatalytic Activity of Cathodes of Solid Oxide Fuel Cells

Chen

Zhao

2013

J. Electrochem. Soc.

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The effect of volatile boron species on the electrocatalytic activity, microstructure and phase stability of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes has been studied. The cathodes were heat-treated at 800 o C for 7 days in air in the presence of boron species vaporized from borosilicate glass, and were characterized by EIS, SEM, AFM, SIMS, XRD, XPS and ICP-OES. The results have shown that after the heat-treatment in the presence of borosilicate glass, boron deposition occurs mainly on the region near electrode surface, leading to the significant Ba and in particular Sr segregation, microstructure change and phase decomposition. On the other hand, the microstructure of the inner electrode layer is almost intact. Electrode polarization resistance, R E , of an as-prepared BSCF cathode is 0.93 and 0.23 Ω cm 2 at 650 and 800 o C, respectively, and changes to 2.08 and 0.15 Ω cm 2 after * Corresponding author. Tel.: +61 8 9266 9804; fax: +61 8 9266 1138. Email address: s.jiang@curtin.edu.au (S.P. Jiang). 1 heat-treatment at 800 o C for 7 days in the presence of borosilicate glass, respectively. The increase in R E for the O 2 reduction reaction on BSCF is much lower than that observed on La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathodes, indicating that BSCF cathodes have a much better tolerance towards boron deposition and poisoning. The limited attack of volatile boron species on BSCF is most likely related to the much slower kinetics of the formation of strontium and barium borates as compared to the formation of lanthanum borates. This study provides a significant insight into design and development of better contaminant-tolerant cathode materials for durable solid oxide fuel cell (SOFC) technologies.

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“…Nonetheless, several investigations concerning the determination of the interaction of CO 2 with BSCF have been continuously carried out, taking the good conductivity of the mixed oxygen ionic and electronic (MIEC) BSCF materials in account . Previous results have shown that high oxygen permeability could be reached with BSCF membranes but, at the same time, that BSCF would display instability with respect to CO 2 . For instance, Park et al .…”

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confidence: 99%

“…At the moment, however, the main drawback is the poor chemical stability of BSCF under CO 2 atmospheres, which are the required operating conditions of their specific application using hydrocarbons . Nonetheless, several investigations concerning the determination of the interaction of CO 2 with BSCF have been continuously carried out, taking the good conductivity of the mixed oxygen ionic and electronic (MIEC) BSCF materials in account . Previous results have shown that high oxygen permeability could be reached with BSCF membranes but, at the same time, that BSCF would display instability with respect to CO 2 .…”

mentioning

confidence: 99%

Oxygen Permeation Properties of La_0.₆Sr₀_.₄Ti₀_.₃Fe₀_.₇O₃_–_d‐Coated Ba_0.₅Sr₀_.₅Co₀_.₈Fe₀_.₂O₃_–_d Disk‐Shaped

Magnone

Kim

Lee

et al. 2015

Bulletin Korean Chem Soc

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Extensive efforts have been devoted during the past years to study the oxygen separation process of perovskite-type membranes at high temperatures and, today, Ba 0.5 Sr 0.5 Co 0.8 -Fe 0.2 O 3-d (BSCF) is considered to be one of the most promising advanced materials for applications in the areas of membrane separation technologies. [1][2][3] At the moment, however, the main drawback is the poor chemical stability of BSCF under CO 2 atmospheres, which are the required operating conditions of their specific application using hydrocarbons. 4-6 Nonetheless, several investigations concerning the determination of the interaction of CO 2 with BSCF have been continuously carried out, taking the good conductivity of the mixed oxygen ionic and electronic (MIEC) BSCF materials in account. [3][4][5][6][7][8][9] Previous results have shown that high oxygen permeability could be reached with BSCF membranes but, at the same time, that BSCF would display instability with respect to CO 2 . 7,8 For instance, Park et al. showed a decrease of the oxygen permeation rate with even a small amount of CO 2 (300 ppm) in synthetic air. 9 The poisoning effect of CO 2 was found to be related to the fact that alkaline-earth metals tend to form carbonates. In fact, the mechanism was described in terms of the formation of a (Ba x Sr 1-x )CO 3 layer on the BSCF membrane surface in CO 2 atmospheres. 8 According to the authors, these mixed barium-strontium carbonates are responsible of decreasing the oxygen permeation flux properties of BSCF membranes. 8 Indisputably, there have not been enough investigations on the protection of the BSCF from the problematic gas components such as CO 2 . With this in mind, we carried out research on A 1−x Sr x M 1−y Fe y O 3−δ -based oxides (A=La, Ba; M=Co, Ti) 9-13 and its outcome. This communication relates to the utilization of La 0.6 Sr 0.4 Ti 0.3 Fe 0.7 O 3-d (LSTF) protective films on the surface of disk-shaped BSCF perovskite oxygen-permeable membrane. One of the main reasons why the LSTF protective film material was chosen was that it has excellent structural stability in CO 2 atmospheres, 10,11 and good performances are seen when using single tubular BSCF membranes 12 as well as tubular modules with LSTF-coated BSCF membranes. 13 Here, the analysis aims (1) to illustrate the oxygen permeation properties of LSTF-coated BSCF disk-shaped membranes in comparison with those of traditional BSCF membranes 9 as a function of temperature (700-950 C) and (2) to elucidate the protective nature of LSTF in the BSCF oxide with particular attention to their applications as MIEC membranes for oxygen separation. A comparative understanding on LSTF protective films on the surface of disk-shaped BSCF perovskite oxygenpermeable membrane is important for perceiving the massive employment of BSCF membranes in the market of oxygenenriched CO 2 stream. 13Experimental BSCF and LSTF oxides were synthesized by the polymerized complex method, followed by calcinations at 1000 and 800 C, respectively. 9,11 The structural properties of...

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AFM investigations on the influence of CO2 exposure on Ba0.5Sr0.5Co0.8Fe0.2O3–δ

Cited by 10 publications

References 33 publications

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Effect of Volatile Boron Species on the Electrocatalytic Activity of Cathodes of Solid Oxide Fuel Cells

Oxygen Permeation Properties of La_0.₆Sr₀_.₄Ti₀_.₃Fe₀_.₇O₃_–_d‐Coated Ba_0.₅Sr₀_.₅Co₀_.₈Fe₀_.₂O₃_–_d Disk‐Shaped

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AFM investigations on the influence of CO2 exposure on Ba0.5Sr0.5Co0.8Fe0.2O3–δ

Cited by 10 publications

References 33 publications

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Effect of Volatile Boron Species on the Electrocatalytic Activity of Cathodes of Solid Oxide Fuel Cells

Oxygen Permeation Properties of La0.6Sr0.4Ti0.3Fe0.7O3–d‐Coated Ba0.5Sr0.5Co0.8Fe0.2O3–d Disk‐Shaped

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Oxygen Permeation Properties of La_0.₆Sr₀_.₄Ti₀_.₃Fe₀_.₇O₃_–_d‐Coated Ba_0.₅Sr₀_.₅Co₀_.₈Fe₀_.₂O₃_–_d Disk‐Shaped