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Investigation of BSCF Cathode on GDC Electrolyte for Intermediate Temperature SOFCs

Investigation of BSCF Cathode on GDC Electrolyte for Intermediate Temperature SOFCs. Vann Brasher. Mentors: Dr. Daniel Mumm Anh Duong Sungrok Bang. The General Outline. The SOFC Synthesis of Samples Testing Conclusion/Future Work. The SOFC. Electrochemistry ½ O 2 + 2 e -  O 2-

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Investigation of BSCF Cathode on GDC Electrolyte for Intermediate Temperature SOFCs

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  1. Investigation of BSCF Cathode on GDC Electrolyte for Intermediate Temperature SOFCs Vann Brasher Mentors: Dr. Daniel Mumm Anh Duong Sungrok Bang

  2. The General Outline • The SOFC • Synthesis of Samples • Testing • Conclusion/Future Work

  3. The SOFC • Electrochemistry • ½ O2 + 2 e-  O2- • O2- + H2  H2O + 2 e- • Conductivity Requirements • Electrolyte O- • Cathode/Anode e- • Solid State Ceramics

  4. The SOFC • Fuel Cell Problems/Voltage Losses • Electrochemical Activation (Overpotential) porosity mixed conductivity • Ohmic thin layers/materials • Mass Transport gas flow system

  5. The SOFC • Purely Electronic Conducting Cathode (LSM) • Triple Phase Boundary limitations • Mixed Conduction (LSF, LSCF) • Incompatible with YSZ!

  6. GNP Synthesis of Samples

  7. B.5S.5CxF1-xO3-δ X=.2,.5,.75 Pm3m cubic Red=Oxygen Green=A-site Ba, Sr Blue=B-site Co, Fe Synthesis of Samples

  8. Screen printing on isostatically pressed GDC BSCF + binder 1cm2 symmetric (both sides) calcine + fast, cheap + simulates industry - inconsistant (ink, blades) Synthesis of Samples

  9. X-Ray Diffraction Identification XRD database published XRD Lattice parameter Bragg’s Law Increase with Co Oxygen vacancy Testing

  10. SEM imaging Visual Characterization Porosity Nano-Scale Features Surface Area Uniformity Testing

  11. Testing • Symmetric Cell Tests • Impedance (10mV AC) from 350-550 °C • DC voltage + Impedance from 600-750 °C • V - iR = η

  12. Testing

  13. Conclusion • Overpotential is a measure of losses due to electrochemical activity at the cathode. • BSCF557525 has lower overpotential better for applications in SOFC cathode. • Can be linked to lattice expansion. More oxygen vacancies, larger cations, etc.

  14. Future Work • Screenprint with consistency and quality • Achieve consistent Impedance data • More samples, aim for repeatability • Compare with other materials • Analyze factors related to overpotential (i.e. porosity, surface area) • Full Cells?

  15. Take it Away! • Fuel Cells are efficient & clean • Mixed Conductors make good Cathodes • Making & Testing Cells takes many steps! • Cobalt increases eletrochemical efficiency

  16. Acknowledgements • National Science Foundation • Dr. Mumm & Lab (Anh, Sungrok) • Said & UROP

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