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Hydrogen Storage in Ti-doped NaAlH4

Hydrogen Storage in Ti-doped NaAlH4. William Gempel. National Hydrogen Initiative. President Bush has proposed $1.2 billion over the next five years to support a new Hydrogen Fuel Initiative. Elements of a Hydrogen Energy Infrastructure. Production Delivery Storage

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Hydrogen Storage in Ti-doped NaAlH4

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  1. Hydrogen Storagein Ti-doped NaAlH4 William Gempel

  2. National Hydrogen Initiative President Bush has proposed $1.2 billion over the next five years to support a new Hydrogen Fuel Initiative.

  3. Elements of a Hydrogen Energy Infrastructure • Production • Delivery • Storage • Conversion • Applications

  4. Hydrogen Storage Methods • High Pressure Tanks • Liquid Hydrogen • Carbon Nanotube Surface Absorbtion • MgH2 • NaAlH4

  5. Comparison of Methods

  6. Reversible Hydrogen Exchange in Metal Hydrides • H2 absorbed under pressure • H atoms bond to metal • H2 released at elevated temperature

  7. Sodium Alanate • 3NaAlH4 -> Na3AlH6 + 2Al +3H2 • Na3AlH6 -> 3NaH + Al + 3/2H2 • 5.6 % Hydrogen by Weight • $50 per kg • Slow Kinetics • Reversible only at ~600 K

  8. Ti-Doped Sodium Alanate • Reversible at ~450 K • Kinetics 2-4 times faster • Still unsatisfactory, but • Working model for possibility of catalytic improvement

  9. Sodium Alanate Structure • Body Centered Tetragonal • Space Group IA/4 • Lattice ~5x11 Ang.

  10. First Principle Calculations forSodium Alanate • Geometry • Electronic Structure • Energy of Formation

  11. First Principles Calculationsfor Ti-Doping • Structurally Stable • Ti Prefers to Substitute for Na • Ti Softens Al-H bonds • It is energetically favorable for Ti to drag extra H into the system

  12. First Principle Studies of Analogous Systems • MxH • Electronic Structure • Energy of Formation • Cohesive Energy • Metal-Hydrogen Bond Strength

  13. Local Projects • Comparing CASTEP to VASP • Reproducing Calculations in Literature • Sodium Alanate Structure (In Progress) • Energy of Formation • Titanium Valence (Population Analysis)?

  14. Conclusion • Ti – Doped Sodium Alanate Experiments show that Catalytic methods can be used to improve operation of Metal Hydrides • First Principle Calculations may lead to understanding of mechanism that will allow improved Catalytic Methods

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