Journal of the Korean Ceramic Society (한국세라믹학회지)

The Korean Ceramic Society (한국세라믹학회)
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Effect of Cathode Porosity on the Cathodic Polarization Behavior of Mixed Conducting LSCF(La0.6Sr0.4Co0.2Fe0.8O3)

혼합전도체 LSCF(La0.6Sr0.4Co0.2Fe0.8O3) 양극의 기공률에 따른 양극분극 특성

  • Yun, Joong-Cheul (Department of Materials Science and Engineering, Korea University, Nano-Materials Research Center, KIST) ;
  • Lee, Jong-Ho (Nano-Materials Research Center, KIST) ;
  • Kim, Joosun (Nano-Materials Research Center, KIST) ;
  • Lee, Hae-Weon (Nano-Materials Research Center, KIST) ;
  • Kim, Byong-Ho (Department of Materials Science and Engineering, Korea University)
  • 윤중철 (고려대학교 재료공학과, 한국과학기술연구원 나노재료연구센터) ;
  • 이종호 (한국과학기술연구원 나노재료연구센터) ;
  • 김주선 (한국과학기술연구원 나노재료연구센터) ;
  • 이해원 (한국과학기술연구원 나노재료연구센터) ;
  • 김병호 (고려대학교 재료공학과)
  • Published : 2005.04.01
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Abstract

In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

혼합전도체 산화물, LSCF의 전극반응점 분포에 따른 분극현상을 관찰하기 위해 다공성 양극의 기공률을 변화시켜가며 분극특성을 관찰하였다. 전극의 기공률을 달리하기 위해 크기가 다른 두 종류의 LSCF 분말들을 혼합비를 달리하여 사용하였으며 GDC 전해질 기판에 스크린 인쇄법을 통해 전극을 구성한 후 반쪽전지 실험을 수행하였다. 제조된 후막전극의 기공률은 화상 분석법을 통해 측정하였으며 전극의 전체 비표면적을 유추하기 위해 2차원 이미지에서의 기공의 둘레 길이를 측정하였다. 교류 임피던스법을 이용해 분극 특성을 관찰한 결과 혼합전도체인 LSCF 양극에서의 전극반응은 i) 양극표면에서 이온화된 산소이온이 전해질과의 삼상계면까지 이동해 오는 단계, ii) 이동해온 산소이온이 양극으로부터 전해질로 전달되는 반응단계에 의해 제어됨을 알 수 있었다. 이러한 양극에서의 분극은 기공률의 증가에 따라 전극 반응에 필요한 활성 표면이 증가됨으로써 줄어드는 것을 알 수 있었다.

Keywords

References

  1. N. Q. Minh, ' Ceramics Fuel Cell,' J. Am. Ceram. Soc., 76 [3] 563-88 (1993) https://doi.org/10.1111/j.1151-2916.1993.tb03645.x
  2. A. B. Stambouli and Traversa, ' Solid Oxide Fuel Cells (SOFCs) : A Review of an Environmentally Clean and Efficient Source of Energy,' Renewable and Sustainable Energy Reviews, 6 433-55 (2002) https://doi.org/10.1016/S1364-0321(02)00014-X
  3. B. C. H. Steele, ' Materials for IT-SOFC Stacks 35 years R&D : The Inevitability of Gradualness?,' Solid State Ionics, 134 3-20 (2000) https://doi.org/10.1016/S0167-2738(00)00709-8
  4. B. C. H. Steele, ' Ceramic Ion Conducting Membranes,' Current Opinion in Solid State & Mater. Sci., 1 684-91 (1996) https://doi.org/10.1016/S1359-0286(96)80052-0
  5. A. Esquirol, N. P. Brandon, J. A. Kilner, and M. Mogensen, ' Electrochemical Characterization of $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3}$ Cathodes for Intermediate-Temperature SOFCs,' J. Electrochemical Soc., 151 [11] A1847-A55 (2004) https://doi.org/10.1149/1.1799391
  6. S. Diethelm and J. V. Herle, ' Oxygen Transport Through Dense $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3}$ Perovskite-Type Permeation Membranes,' J. European Ceram. Soc., 24 1319-23 (2004) https://doi.org/10.1016/S0955-2219(03)00503-X
  7. F. H. van Heuveln, F. P. F. van Berkel, and J. P. P. Huijsmans, ' Characterization of Solid Oxide Fuel Cell Electrodes by Impedance Spectroscopy and I-V Characteristics,' Solid State Ionics, 72, 240-47 (1994) https://doi.org/10.1016/0167-2738(94)90153-8
  8. F. H. van Heuveln and H. J. M. Bouwmeester, ' Electrode Properties of Sr-Doped $LaMnO_{3}$ on Yttria-Stabilized Zirconia,' J. Electrochem. Soc., 144 133-40 (1997) https://doi.org/10.1149/1.1837700
  9. H. Y. Lee, W. S. Cho, S. M. Oh, H. D. Wiemhofer, and W. Gopel, ' Active Reaction Sites for Oxygen Reduction in $La_{0.9}Sr_{0.1}MnO_{3}$/YSZ Electrodes,' J. Electrochem. Soc., 142 [8] (1995)
  10. J. D. Kim, G. D. Kim, J. W. Moon, Y. I. Park, W. H. Lee, K. Kobayashi, M. Nagai, and C. E. Kim, ' Characterization of LSM-YSZ Composite Electrode by AC Impedance Spectroscopy,' Solid State Ionics, 143 379-89 (2001) https://doi.org/10.1016/S0167-2738(01)00877-3
  11. M. Liu and J. Winnick, ' Fundamental Issues in Modeling of Mixed Ionic-Electronic Conductors (MlECs),' Solid State Ionics, 118 11-21 (1999) https://doi.org/10.1016/S0167-2738(98)00451-2
  12. J. Fleig, ' On the Width of the Electrochemically Active Region in Mixed Conducting Solid Oxide Fuel Cell Cath-odes,' J. Power Sources, 105 228-38 (2002) https://doi.org/10.1016/S0378-7753(01)00944-2
  13. J. C. Russ, The Image Processing Handbook, 2nd Edition, pp. 481-546, CRC Press, Boca Raton, 1995
  14. G. Hsieh, G. J. Ford, T. O. Mason, and L. R. Pederson, ' Experimental Limitations in Impedance Spectroscopy: Part I-Simulation of Reference Electrode Artifacts in Three-Point Measurements,' Solid State Ionics, 91 191-201 (1996) https://doi.org/10.1016/S0167-2738(96)00481-X
  15. G. Hsieh, G. J. Ford, T. O. Mason, and L. R. Pederson, ' Experimental Limitations in Impedance Spectroscopy: Part 2-Electrode Artifacts in Three-Point Measurements on Pt/YSZ,' Solid State Ionics, 91 203-12 (1996) https://doi.org/10.1016/S0167-2738(96)00403-1
  16. G. Hsieh, T. O. Mason, E. J. Garboczi, and L. R. Pederson, 'Experimental Limitations in Impedance Spectroscopy : Part 3-Effect of Reference Electrode Geometry/Position,' Solid State Ionics, 96 153-72 (1997) https://doi.org/10.1016/S0167-2738(97)00073-8
  17. J. R. Macdonald, ' Impedance Spectroscopy: Emphasizin Solid Materials and Systems,' pp. 1-26, 84-132, John Wiley &Sons, New York, 1987
  18. J. E. Bauerle, ' Study of Solid Electrolyte Polarization by a Complex Admittance Method,' J. Phys. Chem. Solids, 30 2657-70 (1969) https://doi.org/10.1016/0022-3697(69)90039-0
  19. S. P. Jiang, J. G. Love, J. P. Zhang, M. Hoang, Y. Ramprakash, A. E. Hughes, and S. P. S. Bandwal, ' The Electrochemical Performance of LSM/Zirconia-Yttria Interface as a Function of A-Site Non-Stoichiometry and Cathodic Current Treatment,' Solid State Ionics, 121 1-10 (1999) https://doi.org/10.1016/S0167-2738(98)00295-1