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  • Lee, Hae-Weon  (7)
  • Unknown  (7)
  • 1
    Online Resource
    Online Resource
    The Electrochemical Society ; 2017
    In:  ECS Meeting Abstracts Vol. MA2017-03, No. 1 ( 2017-07-01), p. 223-223
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2017-03, No. 1 ( 2017-07-01), p. 223-223
    Abstract: Solid oxide fuel cells (SOFCs) represent one of the most environmentally friendly and versatile technologies for generation of electrical power and heat from a variety of fuels through electrochemical reactions. Currently, one of the major challenges for commercialization of SOFC technology is the lack of long-term reliability at high temperatures. Especially the high-temperature degradation of SOFC materials with respect to contaminants, structural degradation and material decomposition is known to be the main cause of poor reliability of SOFCs which makes significantly mitigating a broad implementation of SOFCs. Thus, a fundamental understanding of the degradation mechanisms of SOFC materials is needed to find the best degradation mitigation strategies and apply them in order to advance the commercialization of SOFCs. Among many sources of degradation of solid oxide fuel cells (SOFCs), chromium poisoning of cathode has been one of the major concerns for commercial development and deployment. Chromium evaporates from the metallic components of the stack and system in oxidizing atmosphere, and deposits on the active sites of the cathode, leading to degradation of electrode performance. One of the most general approaches to suppress chromium poisoning is to cover the metallic components with protective coating, and various coating materials and deposition techniques have been proposed. However, it is difficult to form sufficiently dense and stable coating on entire part of the potential chromium source of the system. Therefore, solely relying on protective coating for suppression of chromium poisoning is not considered to be reliable, and it is desirable to have additional means to further block chromium vapor from reaching cathode. In this presentation, effect of chromium poisoning on cathode reaction was studied using impedance spectroscopy to illuminate the degradation process in SOFC cathode. From this investigation, especially focused on the air side of SOFCs which occupies the largest portion of SOFC deterioration, we want to identify the underlying degradation mechanisms and propose possible mitigation strategies based on our experimental results.
    Type of Medium: Online Resource
    ISSN: 2151-2043
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2017
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  • 2
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-02, No. 39 ( 2016-09-01), p. 2897-2897
    Abstract: There have been intensive research activities to lower the operating temperature of solid oxide fuel cells (SOFC) to avoid problems related to the high-temperature (≥ 800 o C) operation, such as reliability and cost issues, and to expand the application fields toward portable and mobile power sources. In this regard, thin-film electrolytes and nanostructure electrodes have been at the center of interests to reduce the ohmic and polarization losses while decreasing the operating temperatures. The effect of thinning down the electrolyte is straightforward, however, that of particle size reduction at the electrode is rather complicated. One of the main reasons is the difficulty of elucidating various electrode reaction mechanisms. Another reason can be the difficulty of fabricating the nanostructure electrodes. If conventional powder processing is used, it is challenging to reduce the electrode particle size due to the original particle size of the starting powder and high-temperature sintering. On the other hand, in common thin-film-based SOFCs, nanostructure noble metal electrodes, such as Pt, are employed, thus it is difficult to interrogate the effect of the particle size reduction of the widely used SOFC electrodes.    Owing to the research efforts during the last decade, we have been able to obtain high-performance low-temperature-operating SOFCs (LT-SOFCs) based on the anode-supported platform by implementing thin-film electrolytes and nanostructure electrodes, while using the common SOFC materials. A peak power density as high as 600 mW cm -2 at 500 o C was achieved based on the nanostructure Ni-YSZ anode, ~1 micron-thick YSZ-GDC bilayer electrolyte, and nanostructure LSC or LSC-GDC composite cathode. The active cell components are fabricated by using pulsed laser deposition (PLD) and the particle size of the anode is 100-200 nm, that of the cathode is around 10-several 10s nm. Since the most interested topic regarding the LT-SOFCs has been the cell power output, the study on the effect of nanostructure electrodes at LT is rather not intensively performed. Therefore, in the current presentation, we will exhaustively review and discuss the impact and influence of the particle size reduction to nanoscale at both the cathode and the anode on LT-SOFCs. The distinctive characteristics of the nanoscale electrodes will be presented based on the half-cell and full-cell tests, and the direct comparisons between the cells in which the only difference is the electrode particle size. Acknowledgement The authors are grateful to the Global Frontier R & D Program on Center for Multiscale Energy Systems (Grant No. NRF-2015M3A6A7065442) of the National Research Foundation (NRF) of Korea funded by the Ministry of Science, ICT & Future Planning (MSIP), and to the Institutional Program (2E26081) of Korea Institute of Science and Technology (KIST) for financial support. References J.-H. Park, W.-S. Hong, G. C. Kim, H. J. Chang, J.-H. Lee, K. J. Yoon, and J.-W. Son, J. Electrochem. Soc , 160 , F1027 (2013) H.-S. Noh, K. J. Yoon, B.-K. Kim, H.-J. Je, H.-W. Lee, J.-H. Lee, and J.-W. Son, J. Power Sources , 247 , 105 (2014) J.-H. Park, W.-S. Hong, K. J. Yoon, J.-H. Lee, H.-W. Lee, and J.-W. Son, J. Electrochem. Soc. , 161 , F16 (2014) J. H. Park, S. M. Han, K. J. Yoon, H. Kim, J. Hong, B.-K. Kim, J.-H. Lee, and J.-W. Son, J. Power Sources , 315 , 324 (2016)
    Type of Medium: Online Resource
    ISSN: 2151-2043
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2016
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  • 3
    Online Resource
    Online Resource
    The Electrochemical Society ; 2013
    In:  ECS Transactions Vol. 57, No. 1 ( 2013-10-06), p. 905-910
    In: ECS Transactions, The Electrochemical Society, Vol. 57, No. 1 ( 2013-10-06), p. 905-910
    Abstract: Protonic ceramic fuel cells (PCFCs) based on BaZr 1-x Y x O 3-δ (BZY) have attracted great attention as an alternative for the conventional high temperature fuel cells based on oxygen conducting electrolyte. However, this BZY-based PCFC technology still has many technical problems, especially related with the poor sinterability of BZY electrolytes. In order to overcome this poor sinterability which is a critical limitation in making a thin and dense electrolyte layer for anode-supported PCFCs, we employe the sintering aid-assisted enhanced sintering of BaZr 0.85 Y 0.15 O 3-δ (BZY). We also promote the densification of BZY layer by utilizing the higher sinterability of BaCe 0.9 Y 0.1 O 3-δ (BCY) that is attached to the top of BZY layer. From proper adjusting of the shrinkage behaviors of both anode substrate and dual electrolyte layer, we could fabricate fairly dense BZY/BCY electrolyte layer with less than 10 micro-meter thickness.
    Type of Medium: Online Resource
    ISSN: 1938-5862 , 1938-6737
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2013
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  • 4
    Online Resource
    Online Resource
    The Electrochemical Society ; 2013
    In:  ECS Transactions Vol. 57, No. 1 ( 2013-10-06), p. 3099-3104
    In: ECS Transactions, The Electrochemical Society, Vol. 57, No. 1 ( 2013-10-06), p. 3099-3104
    Abstract: Solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), which are composed of Ni-yttria-stabilized zirconia (YSZ) fuel electrode, YSZ electrolyte, gadolinia-doped ceria (GDC) interdiffusion barrier layer, and (La 0.8 Sr 0.2 ) 0.95 Co 0.2 Fe 0.8 O 3 (LSCF) air electrode, were fabricated and electrochemically tested. The performance of SOEC was dominated by the concentration polarization of the fuel electrode and activation polarization of the air electrode. The concentration polarization of the fuel electrode was reduced by optimization of the pore structure, and the eletrocatalytic activity of the air electrode was enhanced by infiltration of nanocatalysts into the porous electrodes. The cells showed excellent long-term stability up to 300 hour operation.
    Type of Medium: Online Resource
    ISSN: 1938-5862 , 1938-6737
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2013
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  • 5
    In: ECS Transactions, The Electrochemical Society, Vol. 57, No. 1 ( 2013-10-06), p. 885-890
    Abstract: Solid oxide fuel cell is a composite of composites, and goes through a series of composite processing. SOFC always experience extensive constrained sintering in co-firing and post-firing due to shrinkage mismatches. Even though constraints are internal, external, or in combination, SOFCs suffer from critical flaws without optimization of constrained sintering. Thus it is necessary to understand the effects of internal and external constraints on sintering and microstructure development. In this study, we present examples and mechanistic explanation in which critical process flaws were suppressed by hierarchical functional control of the powder packing structure in the viewpoint of constrained sintering.
    Type of Medium: Online Resource
    ISSN: 1938-5862 , 1938-6737
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2013
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  • 6
    Online Resource
    Online Resource
    The Electrochemical Society ; 2013
    In:  ECS Transactions Vol. 57, No. 1 ( 2013-10-06), p. 2357-2364
    In: ECS Transactions, The Electrochemical Society, Vol. 57, No. 1 ( 2013-10-06), p. 2357-2364
    Abstract: The nano-sized YSZ and nano-sized Al 2 O 3 powders were added to a SrO-Al 2 O 3 -B 2 O 3 -SiO 2 glass system to control the effective viscosity and glass retention. Added filler particles evidently improved glass retention. YSZ/glass composites hardly devitrified after heat treating at 800 o C for 100 hours but Al 2 O 3 /glass composites easily devitrified. The devitrified phase, SrAl 2 Si 2 O 8 , decreased the CTE of Al 2 O 3 /glass composite to 5.6x10 -6 / o C. Corrosion of Crofer22/APU was more severe due to contact with Al 2 O 3 /glass composite than with YSZ/glass composite. YSZ composite/glass showed the reliable sealing capability in long-term operation and repeated thermal cycles while the sealing of Al 2 O 3 /glass composite failed during thermal cycling. Such failure of Al 2 O 3 /glass composite was caused not only by the large thermal mismatch between Crofer22APU jig and sealing tape but also by intensifid corrosion of Crofer22APU.
    Type of Medium: Online Resource
    ISSN: 1938-5862 , 1938-6737
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2013
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  • 7
    Online Resource
    Online Resource
    The Electrochemical Society ; 2013
    In:  ECS Transactions Vol. 57, No. 1 ( 2013-10-06), p. 969-973
    In: ECS Transactions, The Electrochemical Society, Vol. 57, No. 1 ( 2013-10-06), p. 969-973
    Abstract: Thin-film electrolytes and nano-structure electrodes are essential components to lower the operation temperature of SOFCs. We will discuss how to precisely assess the impact of the thin-film electrolyte and the nano-structure electrodes which are realized on the anode supports, a realistic SOFC platform (anode-supported TF-SOFC). A peak power density over 500 mWcm -2 at 500 o C is obtained, which we believe is nearing the highest level that the SOFC can reach while using the common SOFC materials and platforms, by changing the dimension of the cell components. The potential and limitations of anode-supported TF-SOFCs in achieving the critical low-temperature performance will be discussed.
    Type of Medium: Online Resource
    ISSN: 1938-5862 , 1938-6737
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2013
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