(259b) 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.