Christine James University of Michigan, Department of Chemical Engineering

1. Atomic Layer Deposition of Zirconium Oxide for Fuel Cell ApplicationsUIC REU – Summer 2011AMReL Lab, UIC Department of Bioengineering andDepartment of Chemical Engineering Christine James University of Michigan, Department of Chemical Engineering

2. Overview • Background • Atomic Layer Deposition • Data Collected • Future Work

3. Fuel Cell Advantages Fossil fuel 2007 • Provides clean energy • Hydrogen fuel cells • only emit water • Very efficient • Fuel Values • Hydrogen: 141.8 kJ/g • Gasoline: 48 kJ/g • Coal: 15-27 kJ/g Santhanam et al., Introduction to Hydrogen Technology, 2009, Hoboken, NJ: J. Wiley. Natural Gas 23 % Coal 23 % Nuclear Power 8 % Renewable Energy 6 % Source: US Energy Information Agency Petroleum 40 % Environmentally friendly

4. Sections of the Fuel Cell SOFC FUEL CELL • Cathode • Oxygen is reduced Electrical Current Fuel In Air In • Electrolyte • Transports the oxygen ions Excess Fuel and Water Unused Gases Out • Anode • Hydrogen is oxidized www1.eere.energy.gov

5. Solid Oxide Fuel Cells (SOFCs) • Current SOFCs are high temperature • Temperature: about 1000 °C • Intermediate Temperature Fuel Cells • Temperature: 600-800°C • Smaller scale applications • Allows use of alternate materials • Starts and stops faster • Reduces corrosion • Offers a wide range of possibilities

6. Problem with Reducing Temperature • High temperatures needed to transport O2- ions • Requirement can be as high as 1200° C • Low temperatures cause ionic resistance Approach • Deposit electrolytes and analyze • Samples from atomic to bulk-like thickness • Method to be used: • Atomic Layer Deposition • Deposit oxide layers on silicon then platinum (Pt)

7. Atomic Layer Deposition (ALD) Methane reaction product CH4 Tri-methyl aluminum Al(CH3)3(g) Methyl group (CH3)3(g) Reaction of TMA with OH Hydroxyl (OH) from surface absorbed H2O H2O www.cambridgenanotech.com/ald

8. Chosen Precursor www.aloha.airliquide.com Niinistö, et al., Advanced Engineering Materials, 2009, 11, No.4, 223.

9. ALD System ZyALD ZyALD

10. Pulse and Purge times required 20 s 10 s Varied Varied 1.5 s 1 s Reactor Temperature: 300°C Bubbler Temperature: 50°C Bubbler Pressure: 10 torr Precursor: ZyALD Precursor Pulse Time: Precursor Purge Time: Oxidizer Pulse Time: Oxidizer Purge Time: Run for 40 cycles Varied 17 s 6 s Varied Zr www.cambridgenanotech.com/ald

11. Temperature Window Reactor Temperature: Varied Bubbler Temperature: 50°C Bubbler Pressure: 10 torr Precursor: ZyALD Temperature Window Precursor Condensation Precursor Decomposition

12. Comparison to Work from another group • Niinistö, et al., J. Mater. Chem. 18, 5243 (2008).

13. Thickness vs. Cycles Run Reactor Temperature: 300°C Bubbler Temperature: 50°C Bubbler Pressure: 10 torr Precursor: ZyALD Slope: .87 R² = 0.9973

14. Future Work • Deposit the zirconium oxide on Platinum • Run electrochemical analysis Electrolyte: Zirconium Oxide Silicon Substrate Platinum

15. Summary • Goal is to lower operating temperature of the fuel cell • By decreasing electrolyte layer thickness • Atomic Layer Deposition (ALD) is being used • Have determined some necessary parameters: • Pulse and Purge times • Temperature Window for ALD • Have compared cycles and thickness • Proved linear relationship • Next Steps: • Deposit on Platinum • Run Electrochemical analysis

16. Acknowledgements • National Science Foundation • EEC-NSF Grant # 1062943 • Graduate Mentor: RunshenXu • Professor Takoudis and Professor Jursich