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Infrared Studies of Ammonia Borane

Infrared Studies of Ammonia Borane. Kevin Meaux. Background. Alternatives to fossil fuels to power transportation are sought To use hydrogen for fuel, a more effective way of storing H 2 is needed High volumetric density, hydrogen mass %, stability, and reversibility are desired

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Infrared Studies of Ammonia Borane

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  1. Infrared Studies of Ammonia Borane Kevin Meaux

  2. Background • Alternatives to fossil fuels to power transportation are sought • To use hydrogen for fuel, a more effective way of storing H2 is needed • High volumetric density, hydrogen mass %, stability, and reversibility are desired • Liquid and gaseous H2 are not dense enough • Metal hydrides and similar compounds offer potential solutions

  3. Ammonia Borane (H3N:BH3) For Comparison… [1] Marder, T., AngewandteChemie International Edition, 2007, 46, 8116–8118.

  4. Goal • For effective use, more info is needed on the dehydrogenation process of ammonia borane(AB) • Important first steps involve developing a working experimental setup to study this change

  5. Analysis Method • Using Transmittance Fourier Transform Infrared Spectroscopy • Characterizes a substance by the vibration of its chemical bonds Infrared Spectroscopy Schematic http://solidstate.physics.sunysb.edu/book/prob/node111.html

  6. Original Experimental Setup • KBr and NH3BH3 are mixed in a 25:1 ratio • KBr alone and the KBr/AB mixture are pressed into a tungsten mesh in different spots • Have varied the reference salt, absolute amounts, and ratios

  7. The IR Cell • Sample is under rough vacuum for analysis (~9E-2 torr) • Heated and then allowed to cool under argon (~5 torr) • New spectra is taken at room temperature and rough vacuum copper leads for resistive heating sample tungsten mesh grid reference Image produced by Oleg Byl

  8. 10%

  9. Peak Comparison Table *This table compares reference IR peaks for ammonia boranewith data gathered for 300K [2] JJ. Smith, K. S. Seshadri, and David White: J. Mol. Spec., 1973, 45, 327-337.

  10. Analysis • The 1126,2225, and 2291 peaks shown forming at 433 K correspond to KBH43 • The 1959/2029 peaks formed at 913 K are likely the formation of B11O2/B10O2 anions 4 • The other peaks observed at 433 K do not fit with borazine, boron oxides, or boron nitride [3] K. B. Harvey and N. R. McQuaker: Canadian Journal of Chemistry, 1971, 49, 3272-3281. [4] I.C. Hisatsune and Noelia Haddock Suarez: Inorganic Chemistry, 1964, 3, 168-174.

  11. Current Sample Prep Idea • Had problems with KBr reactivity in pellet preparation • Instead it is prepared on a KBr window • Dissolved AB in THF • Deposited solution on KBr disk • Boiled off THF (67 C) • Mounted disk onto mesh Thermocouple KBr Window

  12. AB solution deposited on KBr disk

  13. H3N:BH3 at Room Temperature

  14. Analysis • The new sample prep method shows more clearly resolved peaks • The accuracy of temperatures needs to be verified • The peaks are shifted somewhat from literature values • The spectra demonstrates dehydrogenation with heating • Neither the KBH4 nor BO2- peaks are seen

  15. Summary • AB can be useful as a hydrogen storage media • More work needs to be done in characterizing its dehydrogenation • Current method yields noisy spectra but shows potential • Will be dealing with the noise issues in the near future

  16. Acknowledgements This work was supported by the National Science Foundation under EEC-NSF Grant # 1062943 I would like to thank Dr. Trenary and Dr. Jash for their guidance, as well as Dr. Takoudis and Dr. Jursich for administrating the UIC REU program

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