Jeevitha Evanjeline Martin Professor Daniel Mumm Grad Student: Anh Duong August 2 nd , 2006

1. Nanoscale Electrode Development for Fundamental Studies of Mixed Ionic and Electronic Conductors as High Temperature Fuel Cell Components Jeevitha Evanjeline Martin Professor Daniel Mumm Grad Student: Anh Duong August 2nd, 2006

2. Outline • Solid Oxide Fuel Cell • Polarization losses • Triple Phase Boundary • Cathode microstructure • Traditional method for cathode fabrication • Experiment • Results • Discussion • Acknowledgements

3. Solid Oxide Fuel Cell • Solid-state device that uses an oxide-ion conducting ceramic material as the electrolyte. • The high operating temperatures eliminates the use of catalysts. • Oxygen is reduced at the cathode. • Oxygen ion is transported from the cathode to the anode through the electrolyte. • Forms Water. • Perfect candidate for hybrid systems.

4. Overall : H2(g) + ½O2(g) -> H2O(g) Anode: H2(g) + O2- -> H2O(g) + 2e- Cathode: ½O2(g) + 2e- -> O2- Wikipedia

5. Polarization losses • VNernst = -ΔG/2F • F = Faraday’s constant • ΔG = Gibbs free energy for overall cell reaction Dr. Mumm UCSB 2006

6. Importance of Porosity • Allows improved oxygen transport • Increases the TPB available for reaction • LSM (Lanthanum Strontium Manganate) • YSZ (Ytrria Stabilized Zirconia) Adler Chem Rev, 2004

7. Techniques used for the fabrication of Cathode layers • Traditionally GNP. • Glycine Nitrate Process. • Self sustaining combustion synthesis technique. • Produces fine homogeneous metal oxide powders. • Resulting ash is calcined to remove any organics. • Control over the stoichiometry. • Screen printing. • Now exploring: Electrostatic Spray Deposition (ESD).

8. Advantages of ESD • Recently developed. • Employs very fine precursor solution. • Allows the user to control porosity. • Flowrate • Voltage • Temperature • Time • Nozzle to substrate distance

9. Objective • To build ESD setup • To create porous Lanthanum Strontium Manganese Oxide(LSM) electrode layer over stainless steel substrate using Electrostatic Spray Deposition.

10. ESD Solid State Ionics 156 (2003) 1 – 13

11. Precursor solution needed for La0.8Sr0.2MnO3 • Lanthanum Nitrate (0.8) • Strontium Chloride hexahydrate (0.2) • Manganese Nitrate hexahydrate (1) • 33% Ethanol • 67% Butyl Carbitol

12. First try at making the solution • Lanthanum Nitrate • Strontium acetate • Manganese Nitrate + xH2O • Water • 33% Ethanol • 67% Butyl Carbitol NO!

13. Second try at making the solution • Lanthanum Nitrate • Strontium chloride hexahydrate • Manganese Nitrate hexahydrate • 33% Ethanol • 67% Butyl Carbitol NO!

14. Third try at making the solution • Lanthanum Nitrate • Strontium chloride hexahydrate • Manganese Nitrate hexahydrate • 3 drops of water • 33% Ethanol • 67% Butyl Carbitol YES!

15. Parameters for Experiments • Substrate = Stainless steel disk • Nozzle to substrate distance = variable • Voltage = 5kV • Flowrate = 0.5ml/h • Substrate temperature = 573K • Annealed at 1173K for 2hrs

16. Results a) Distance = 12mm c) Distance = 15mm b) Distance = 10 mm d) Distance = 19 mm

17. X-ray Diffraction

18. Discussion • Porosity increases with distance • X-ray Diffraction is compatible with known pattern except sample # 7 which showed contamination and cracks

19. Future work • Vary other parameters • Use YSZ as the substrate • Make layers of cathode while varying the density • Electrochemical characterization • Polarization curve • Impedance spectroscopy

20. Acknowledgements • IMSURE team • Dr. Mumm (ChEMS) • Anh Duong (ChEMS) • Professor Noo Li’s group • Gamma high voltage • National Science Foundation • Carl Zeiss center of excellence