Carbon Assisted Hydrogenation and Dehydrogenation of Lithium Borohydrides

Application of complex metal hydrides as hydrogen storage materials is hampered by the slow hydrogenation and dehydrogenation kinetics.  The presence of high surface area carbon greatly accelerated the dehydrogenation and hydrogenation kinetics of LiBH₄ even when the two components are present only as physical mixtures.   Different synthesis procedures were explored to increase the contact between the two components.  Dehydrogenation kinetics was accelerated for a carbon –LiBH₄ composite synthesized by liquid phase infusion of the carbon pores with 2M solution of LiBH₄, when compared to the physical mixture.   After dehydrogenation, the sample was subjected to a rehydrogenation treatment of 390 ^oC and 14 atmospheres of H _2.   H₂ uptake was observed even under such a mild condition, although only partial reversibility was observed after one hour of hydrogenation.  The sample after the second dehydrogenation was rehydrogenated to about the same extent as the first rehydrogenation.   The ability to effect rehydrogenation under mild conditions and short duration was attributed to a nano-confinement effect.   Ni and Co were added to the carbon and tested as metal catalytic components to further accelerate the hydrogenation and dehydrogenation kinetics.