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Improving the electrolyte/ cathode assembly for advanced Solid Oxide Fuel Cells

Improving the electrolyte/ cathode assembly for advanced Solid Oxide Fuel Cells. N. Hildenbrand , B.A. Boukamp, D.H.A. Blank (a) P. Nammensma, G. Rietveld (b) (a) MESA+ Institute for Nanotechnology (b) Energy research Centre Netherlands. SOFC, a challenge. SOFC, a challenge.

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Improving the electrolyte/ cathode assembly for advanced Solid Oxide Fuel Cells

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  1. Improving the electrolyte/ cathode assembly for advanced Solid Oxide Fuel Cells N. Hildenbrand, B.A. Boukamp, D.H.A. Blank (a) P. Nammensma, G. Rietveld (b) (a) MESA+ Institute for Nanotechnology (b) Energy research Centre Netherlands

  2. SOFC, a challenge

  3. SOFC, a challenge • Power density delivered by SOFC in W/cm2 P = Emf x i – ASR x i2 where - Emf is electromotive force, ca. 1V - i is current density, A/cm2 - ASR is Area Specific Resistance Ω.cm2

  4. SOFC, a challenge • ASR = economic obstacle - Electrolyte and electrode reaction resistances - Gas diffusion limitations - Change of gas compositions - Contact resistance in all interfaces Søren Linderoth, 2007 • Target ASR value: 0.1 Ω.cm2 at the lowest temperature possible.

  5. What brings nanotechnology? • Improveelectrolyte / cathode interface. Porous LSCF, 53 μm Electrolyte 3YSZ, 92 μm Interlayer YDC, 1-4 μm LSCF : La0.6SrO.4Co0.2Fe0.8O3-δ YSZ : Yttira Stabilized Zirconia YDC : Yttria Doped Ceria

  6. What brings nanotechnology? • Combination of dense and porouselectrode Porous LSCF, 53 μm Electrolyte 3YSZ, 92 μm Dense LSCF 200 nm Interlayer YDC, 1-4 μm LSCF : La0.6SrO.4Co0.2Fe0.8O3-δ YSZ : Yttira Stabilized Zirconia YDC : Yttria Doped Ceria

  7. Microstructure • 2 types of microstructure

  8. Microstructure with LSCF as cathode • Sample type P

  9. Microstructure with LSCF as cathode ZOOM • Sample type DP

  10. Microstructure with LSCF as cathode Porous LSCF « Dense » LSCF YDC YSZ N.Hildenbrand, B.A.Boukamp, N.Nammensma, D.H.A.Blank, doi:10.1016/j.ssi.2010.01.028. • Sample type DP

  11. Area Specific Resistance ASR ASR ASR improved by factor 3 Why do we observe such an improvement ???

  12. Analysis e- O2 e- O2 O2- O2- O2- [1] S.B. Adler, J.A. Lane, B.C.H. Steele, J.Electrochem.Soc. 143 (1996) 3554-64 [2] Y. Lu, C. Kreller, S.B. Adler, J.Electrochem.Soc. 156 (2009) B513 • The ALS model [1-2] leads to a Gerischer response. Competition between surface transport and bulk transport. v = surface / bulk transport Limitation by surface exchange and bulk diffusion. Qualitatively: Ds >> Ka +Dv

  13. Impedance characteristics of both cells at 600ºC in air ASR ASR

  14. R-gb R-el’l R-lf R-gd Q-gb Gerischer Q-lf C-gd Feature only at low temperatures and high frequencies Feature only at high temperatures and low frequencies Model: equivalent circuit N.Hildenbrand, B.A.Boukamp, N.Nammensma, D.H.A.Blank, Solid State Ionics, to be submitted.

  15. pO2 dep. op Gerischer parameters at 600°C • Variation as P(O2) to the power m: mP (Ka) = 0.62 (ALS: 0.64) mP (Z0) = 0.17 (ALS: 0.30)

  16. pO2 dep. op Gerischer parameters at 600°C • Variation as P(O2) to the power m: mP (Ka) = 0.62 (ALS: 0.64) mP (Z0) = 0.17 (ALS: 0.30) • Variation as P(O2) to the power m: mDP (Ka) = 0.25 (ALS: 0.64) mDP (Z0) = 0.76 (ALS: 0.30) The mechanism of oxygen reduction is changed!

  17. Analysis - Concept Dv

  18. Analysis - Concept [1] S.B. Adler, J.A. Lane, B.C.H. Steele, J.Electrochem.Soc. 143 (1996) 3554-64 [2] Y. Lu, C. Kreller, S.B. Adler, J.Electrochem.Soc. 156 (2009) B513 Dv Ds >> Dv & Ds >> Ka [1-2] Accumulation of Oad on the surface of the MIEC at the base of each rod.

  19. Analysis - Concept [1] S.B. Adler, J.A. Lane, B.C.H. Steele, J.Electrochem.Soc. 143 (1996) 3554-64 [2] Y. Lu, C. Kreller, S.B. Adler, J.Electrochem.Soc. 156 (2009) B513 Dv Ds >> Dv & Ds >> Ka [1-2] Accumulation of Oadon the surface of the MIEC at the base of each rod.

  20. Analysis - Concept Dv More active sites at the base of each rod for surface exchange.

  21. Analysis - Concept Dv More active sites at the base of each rod for surface exchange.

  22. Conclusion Improvement of the Area Specific Resistance by a factor 3 for LSCF. Decrease working temperature of 75ºC for LSCF. It works for other materials. http://doc.utwente.nl/78272/ The oxygen reduction mechanism is changed Concept to explain this phenomenon.

  23. Outlook • Advanced Dutch Energy Materials Innovation Lab – ADEM projects • Funding by Ministerie van Economische Zaken (EZ). • Collaboration between the 3 TU. • 2 PhD projects within IMS - Advanced materials for SOFC anode. - Development of thin films deposition techniques for SOFC electrolytes.

  24. Acknowledgements Project funded by SenterNovem, agency of the Dutch Ministry of the Economic Affairs, promoting sustainable development and innovation, both within the Netherlands and abroad. IMS group of University of Twente.

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