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. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science SOFC, a challenge

3. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science SOFC, a challenge  Power density delivered by SOFC in W/cm 2 P = E mf x i – ASR x i 2 where - E mf is electromotive force, ca. 1V - i is current density, A/cm 2 - ASR is Area Specific Resistance Ω.cm 2

4. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science 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.cm 2 at the lowest temperature possible.

5. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science  Improve electrolyte / cathode interface. Porous LSCF, 53 μm Interlayer YDC, 1-4 μm Electrolyte 3YSZ, 92 μm What brings nanotechnology? LSCF : La 0.6 Sr O.4 Co 0.2 Fe 0.8 O 3-δ YSZ : Yttira Stabilized Zirconia YDC : Yttria Doped Ceria

6. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science What brings nanotechnology? Porous LSCF, 53 μm Interlayer YDC, 1-4 μm Electrolyte 3YSZ, 92 μm Dense LSCF 200 nm  Combination of dense and porous electrode LSCF : La 0.6 Sr O.4 Co 0.2 Fe 0.8 O 3-δ YSZ : Yttira Stabilized Zirconia YDC : Yttria Doped Ceria

7. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Microstructure  2 types of microstructure

8. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Microstructure with LSCF as cathode  Sample type P

9. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Microstructure with LSCF as cathode  Sample type DP ZOOM

10. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Microstructure with LSCF as cathode  Sample type DP 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.

11. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Area Specific Resistance ASR improved by factor 3 Why do we observe such an improvement ??? ASR

12. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis  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: D s >> K a + D v e-e- O2O2 O 2- e-e- O2O2 [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

13. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Impedance characteristics of both cells at 600ºC in air ASR

14. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Model: equivalent circuit Gerischer Q-lf R-lf C-gd R-gd Feature only at high temperatures and low frequencies R-gb Q-gb R-el’l Feature only at low temperatures and high frequencies N.Hildenbrand, B.A.Boukamp, N.Nammensma, D.H.A.Blank, Solid State Ionics, to be submitted.

15. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science  Variation as P(O 2 ) to the power m: m P (K a ) = 0.62 (ALS: 0.64) m P (Z 0 ) = 0.17 (ALS: 0.30) pO 2 dep. op Gerischer parameters at 600°C

16. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science  Variation as P(O 2 ) to the power m: m P (K a ) = 0.62 (ALS: 0.64) m P (Z 0 ) = 0.17 (ALS: 0.30)  Variation as P(O 2 ) to the power m: m DP (K a ) = 0.25 (ALS: 0.64) m DP (Z 0 ) = 0.76 (ALS: 0.30) The mechanism of oxygen reduction is changed! pO 2 dep. op Gerischer parameters at 600°C

17. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis - Concept DvDv

18. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis - Concept  D s >> D v & D s >> K a [1-2]  Accumulation of O ad on the surface of the MIEC at the base of each rod. [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 DvDv

19. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis - Concept  D s >> D v & D s >> K a [1-2]  Accumulation of O ad on the surface of the MIEC at the base of each rod. [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 DvDv

20. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis - Concept  More active sites at the base of each rod for surface exchange. DvDv

21. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science Analysis - Concept  More active sites at the base of each rod for surface exchange. DvDv

22. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science 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. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science 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. UNIVERSITY OF TWENTE. MESA + Institute for Nanotechnology Inorganic Materials Science 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.