A number of methods and materials have been synthesized for use as hydrogen storage materials. However, to date, none of the materials are capable of being used as a sustainable fuel source as a result of poor recyclability. Therefore, new materials need to be synthesized and evaluated in order to obtain the goal of creating a hydrogen fuel economy. Furthermore, some possible hydrogen storage candidates have been ignored as a result of poor and laborious syntheses. Finding new synthetic routes to these materials opens exploration of their effectiveness as a hydrogen source.
The reaction of lithium aluminum hydride with ammonia borane has been investigated in varying ratios. Evaluation of the hydrogen released, proton and boron-11 NMR spectroscopy, and infrared spectroscopy indicate the formation of a compound of composition LiAl(NHBH3)H2 in the equimolar reaction of lithium aluminum hydride and ammonia borane followed by subsequent addition of amidotrihydroborate to this material with the presence of additional ammonia borane to form LiAl(NHBH3)(NH2BH3)H and LiAl(NHBH3)(NH2BH3)2. It was unclear whether the reaction in a ratio of 1:4 lithium aluminum hydride to ammonia borane produced LiAl(NH2BH3)4 or if the product was identical to that of the reaction in a 1:3 ratio. All of the compounds made retain a high gravimetric capacity of hydrogen.
Solvent-free sodium octahydrotriborate was synthesized via a new method en route to ammonia triborane. Tetrahydrofuran borane complex solution was stirred with an amalgamation of sodium and mercury to produce the solvent coordinated sodium octahydrotriborate and sodium borohydride. The product was separated by extraction with ethyl ether and heating to remove coordinated solvent. Average yield of the final product was approximately 60%.
A literature method for synthesizing ammonia triborane was refined, removing the need for multiple cooling steps and for the use of column chromatography to purify the product. The reaction of elemental iodine with tetrabutylammonium octahydrotriborate was allowed to react at room temperature rather than addition at low temperatures, producing identical results to the literature procedure. Furthermore, the ammonia triborane was separated from the remaining residue after removal of the solvent using a mixed solvent of hexanes and ethyl ether. Potassium octahydrotriborate was also able to be used in the synthesis in place of the tetrabutylammonium salt.