• Title/Summary/Keyword: Solid oxide cells

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Degradation Comparison of Hydrogen and Internally Reformed Methane-Fueled Solid Oxide Fuel Cells

  • Kim, Young Jin;Lee, Hyun Mi;Lim, Hyung-Tae
    • Journal of the Korean Ceramic Society
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    • v.53 no.5
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    • pp.483-488
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    • 2016
  • Anode supported solid oxide fuel cells (SOFCs), consisting of Ni+YSZ anode, YSZ electrolyte, and LSM+YSZ cathode, were fabricated and constant current tested with direct internal reforming of methane (steam to carbon ratio ~ 2) as well as hydrogen fuel at $800^{\circ}C$. The cell, operated under direct internal reforming conditions, showed relatively rapid degradation (~ 1.6 % voltage drop) for 95 h; the cells with hydrogen fuel operated stably for 170 h. Power density and impedance spectra were also measured before and after the tests, and post-test analyses were conducted on the anode parts using SEM / EDS. The results indicate that the performance degradation of the cell operated with internal reforming can be attributed to carbon depositions on the anode, which increase the resistance against anode gas transport and deactivate the Ni catalyst. Thus, the present study shows that direct internal reforming SOFCs cannot be stably operated even under the condition of S/C ratio of ~ 2, probably due to non-uniform mixture (methane and steam) gas flow.

Maximizing TPBs through Ni-self-exsolution on GDC based composite anode in solid oxide fuel cells

  • Tan, Je-Wan;Lee, Dae-Hui;Kim, Bo-Gyeong;Kim, Ju-Seon;Mun, Ju-Ho
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.402.1-402.1
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    • 2016
  • The performance of solid oxide fuel cells (SOFCs) is directly related to the electrocatalytic activity of composite electrodes in which triple phase boundaries (TPBs) of metallic catalyst, oxygen ion conducting support, and gas should be three-dimensionally maximized. The distribution morphology of catalytic nanoparticle dispersed on external surfaces is of key importance for maximized TPBs. Herein in situ grown nickel nanoparticle onto the surface of fluorite oxide is demonstrated employing gadolium-nickel co-doped ceria ($Gd0.2-xNixCe0.8O2-{\delta}$, GNDC) by reductive annealing. GNDC powders were synthesized via a Pechini-type sol-gel process while maximum doping ratio of Ni into the cerium oxide was defined by X-ray diffraction. Subsequently, NiO-GNDC composite were screen printed on the both sides of yttrium-stabilized zirconia (YSZ) pellet to fabricate the symmetrical half cells. Electrochemical impedance spectroscopy (EIS) showed that the polarization resistance was decreased when it was compared to conventional Ni-GDC anode and this effect became greater at lower temperature. Ex situ microstructural analysis using scanning electron microscopy after the reductive annealing exhibited the exsolution of Ni nanoparticles on the fluorite phases. The influence of Ni contents in GNDC on polarization characteristics of anodes were examined by EIS under H2/H2O atmosphere. Finally, the addition of optimized GNDC into the anode functional layer (AFL) dramatically enhanced cell performance of anode-supported coin cells.

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Ceramic Materials for Interconnects in Solid Oxide Fuel Cells - A Review (고체산화물 연료전지 연결재용 세라믹 소재)

  • Park, Beom-Kyeong;Song, Rak-Hyun;Lee, Seung-Bok;Lim, Tak-Hyoung;Park, Seok-Joo;Park, Chong-Ook;Lee, Jong-Won
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.231-242
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    • 2014
  • An interconnect in solid oxide fuel cells (SOFCs) electrically connects unit cells and separates fuel from oxidant in the adjoining cells. The interconnects can be divided broadly into two categories - ceramic and metallic interconnects. A thin and gastight ceramic layer is deposited onto a porous support, and metallic interconnects are coated with conductive ceramics to improve their surface stability. This paper provides a short review on ceramic materials for SOFC interconnects. After a brief discussion of the key requirements for interconnects, the article describes basic aspects of chromites and titanates with a perovskite structure for ceramic interconnects, followed by the introduction of dual-layer interconnects. Then, the paper presents protective coatings based on spinel-or perovskite-type oxides on metallic interconnects, which are capable of mitigating oxide scale growth and inhibiting Cr evaporation.

Solid oxide fuel cell and application of proton conducting ceramics (고체산화물 연료전지와 양성자 전도성 세라믹 물질의 응용)

  • Jeong, Donghwi;Kim, Guntae
    • Ceramist
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    • v.21 no.4
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    • pp.366-377
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    • 2018
  • Solid oxide fuel cells (SOFCs) are promising eco-friendly energy conversion system due to their high efficiency, low pollutant emission and fuel flexibility. High operating temperatures, however, leads to the crucial drawbacks such as incompatibility between the components and high thermal stress. Proton-conducting ceramic fuel cells (PCFCs) with proton-conducting oxide (PCO) materials are new types of fuel cells that can solve the problems of conventional SOFCs. Many studies have been proceeded to improve the performance of electrolytes and electrodes, and triple conductive oxides (TCOs) have attracted significant attention as high performance PCFC electrodes.

Chromium Poisoning of Neodymium Nickelate (Nd2NiO4) Cathodes for Solid Oxide Fuel Cells

  • Lee, Kyoung Jin;Chung, Jae Hun;Lee, Min Jin;Hwang, Hae Jin
    • Journal of the Korean Ceramic Society
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    • v.56 no.2
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    • pp.160-166
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    • 2019
  • In this study, we investigated the long-term stability of Nd2NiO4 solid oxide fuel cell (SOFC) cathodes to evaluate their chromium poisoning tolerance. Symmetrical cells consisting of Nd2NiO4 electrodes and a yttria-stabilized zirconia electrolyte were fabricated and the cell potential and polarization resistance were measured at 850 ℃ in the presence of gaseous chromium species for 800 h. Up to 500 h of operation, the cell potential remained constant at 500 mA/㎠. However, it increased slightly over the operation duration of 550-800 h. No appreciable increase was observed in the polarization resistance of the Nd2NiO4 cathode during the entire operation of 800 h. Physicochemical examinations revealed that the gaseous chromium species did not form chromium-related contamination not only in the Nd2NiO4 cathode but also at the cathode/electrolyte interface. The results demonstrated that Nd2NiO4 is resistant to chromium poisoning, and hence is a potential alternative to standard perovskite cathodes.

Electrical Properties in GDC (Gd2O3-Doped CeO2)/LSCF (La0.6Sr0.4Co0.2Fe0.8O3) Cathode Composites for Intermediate Temperature Solid Oxide Fuel Cells

  • Lee, Hong-Kyeong;Hwang, Jin-Ha
    • Journal of the Korean Ceramic Society
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    • v.48 no.1
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    • pp.110-115
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    • 2011
  • $Gd_2O_3$-doped $CeO_2$ (GDC) and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) composite cathode materials were prepared in order to be applied to intermediate-temperature solid oxide fuel cells. The electrochemical polarization was evaluated using ac impedance spectroscopy involving geometric restriction at the interface between an ionic electrolyte and a mixed-conducting cathode. In order to optimize the cathode composites applicable to a GDC electrolyte, the cathode composites were evaluated in terms of polarization losses with regard to a given electrolyte, i.e., GDC electrolyte. The polarization increased significantly with decreasing temperature and was critically dependent on the compositions of the composite cathodes. The optimized cathode composite was found to consist of GDC 50 wt% and LSCF 50 wt%; the corresponding normalized polarization loss was calculated to be 0.64 at $650^{\circ}C$.

Characterization and Electrochemical Performance of Composite BSCF Cathode for Intermediate-temperature Solid Oxide Fuel Cell

  • Kim, Yu-Mi;Kim-Lohsoontorn, Pattaraporn;Bae, Joong-Myeon
    • Journal of Electrochemical Science and Technology
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    • v.2 no.1
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    • pp.32-38
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    • 2011
  • The composite barium strontium cobalt ferrite (BSCF) cathodes were investigated in the intermediate temperature range of solid oxide fuel cells (SOFCs). The characteristics and electrochemical performances of composited BSCF/samarium doped ceria (SDC); BSCF/gadolinium doped ceria (GDC); and BSCF/SDC/GDC were compared to single BSCF cathode. The BSCF used in this study were synthesized using glycine nitrate process and mechanically mixing was used to fabricate a composite cathode. Using a composite form, the thermal expansion coefficient (TEC) could be reduced and BSCF/SDC/GDC exhibited the lowest TEC value at $18.95{\times}10^{-6}K^{-1}$. The electrochemical performance from half cells and single cells exhibited nearly the same trend. All the composite cathodes gave higher electrochemical performance than the single BSCF cathode (0.22 $Wcm^{-2}$); however, when two kinds of electrolyte were used (BSCF/SDC/GDC, 0.36$Wcm^{-2}$), the electrochemical performance was lower than when the BSCF/SDC (0.45 $Wcm^{-2}$) or BSCF/GDC (0.45 $Wcm^{-2}$) was applied as cathode ($650^{\circ}C$, 97%$H_2$/3%$H_2O$ to the anode and ambient air to the cathode).

Computational Analysis of Transport Phenomena in a Planar-Type Solid Oxide Fuel Cell with a Simplified Treatment of the Electrochemical Heat Generation (전기화학 반응에 의한 생성 열의 단순화된 처리 기법을 이용한 평판형 고체산화물 연료전지 내부의 이동현상에 대한 전산 해석)

  • Cha, Hoon;Sohn, Jeong-Lak;Ro, Sung-Tack
    • Journal of the Korean Ceramic Society
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    • v.42 no.12 s.283
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    • pp.846-853
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    • 2005
  • For the performance prediction of a planar-type solid oxide fuel cell, the computational analysis of transport phenomena with a simplified treatment of heat generation by the electrochemical reaction is conducted. From the result of the computational analysis, it is shown that the electrochemical reaction is closely related to the transport phenomena inside a solid oxide fuel cell. Transport phenomena including heat and mass transfer influences on the distribution of local current density and, as a result, on the performance characteristics of the fuel cell. Computational analysis is also extended to the parametric study to investigate the performance behavior of the fuel cell with different amount of supplied fuel flow rates. It is also demonstrated that the mathematical formulation and computational procedures proposed in this study can be applied to prove the importance of the specific TPB area in the manufacturing process of electrodes in solid oxide fuel cells.

Study on Possibility of PrBaMn2O5+δ as Fuel Electrode Material of Solid Oxide Electrolysis Cell (이중 페로브스카이트 촉매 PrBaMn2O5+δ의 고온전기분해조(Solid Oxide Electrolysis Cell) 연료극 촉매로 적용 가능성에 대한 연구)

  • Kwon, Youngjin;Kim, Dongyeon;Bae, Joongmyeon
    • Journal of the Korea Institute of Military Science and Technology
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    • v.20 no.4
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    • pp.491-496
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    • 2017
  • The hydrogen($H_2$) is promising energy carrier of renewable energy in the microgrid system such as small village and military base due to its high energy density, pure emission and convenient transportation. $H_2$ can be generated by photocatalytic water splitting, gasification of biomass and water electrolysis driven by solar cell or wind turbine. Solid oxide electrolysis cells(SOECs) are the most efficient way to mass production due to high operating temperature improving the electrode kinetics and reducing the electrolyte resistance. The SOECs are consist of nickel-yttria stabilized zirconia(NiO-YSZ) fuel electrode / YSZ electrolyte / lanthanum strontium manganite-YSZ(LSM-YSZ) air electrode due to similarity to Solid Oxide Fuel Cells(SOFCs). The Ni-YSZ most widely used fuel electrode shows several problems at SOEC mode such as degradation of the fuel electrode because of Ni particle's redox reaction and agglomeration. Therefore Ni-YSZ need to be replaced to an alternative fuel electrode material. In this study, We studied on the Double perovskite $PrBrMnO_{5+{\delta}}$(PBMO) due to its high electric conductivity, catalytic activity and electrochemical stability. PBMO was impregnated into the scaffold electrolyte $La_{0.8}Sr_{0.2}Ga_{0.85}Mg_{0.15}O_{3-{\delta}}$(LSGM) to be synthesized at low temperature for avoiding secondary phase generated when it exposed to high temperature. The Half cell test was conducted at SOECs and SOFCs modes.

Fabrication of LaySr1-yFexTi1-xO3-based Nanocomposite Solid Oxide Fuel Cell Anodes by Infiltration (Infiltration법을 이용한 LaySr1-yFexTi1-xO3계 나노복합 연료극 제조)

  • Yoon, Jong-Seol;Choe, Yeong-Ju;Hwang, Hae-Jin
    • Journal of the Korean Ceramic Society
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    • v.51 no.3
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    • pp.224-230
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    • 2014
  • Nano-sized gadolinium-doped ceria (GDC)/nickel particle-dispersed $La_ySr_{1-y}Ti_{1-x}Fe_xO_3$ (LSFTO)-based composite solid oxide fuel cell anodes were fabricated by an infiltration method and the effects of the GDC/Ni nanoparticles on the anode polarization resistance and cell performance were investigated in terms of the infiltration time and nickel content. The anodic polarization resistance of the LSFTO anode was significantly enhanced by GDC and/or Ni infiltration and it decreased with increasing infiltration time and Ni content, respectively. It is believed that the observed phenomena are associated with enhancement of the ionic conductivity and catalytic activity in the nanocomposite anodes by the addition of GDC and Ni. Power densities of cells with the LSFTO and LSFTO-GDC/Ni nanocomposite anodes were 150 and $300mW/cm^2$ at $800^{\circ}C$, respectively.