(657c) Complex Borohydride for Reversible Hydrogen Storage

Materials that are light weight, low cost and have high hydrogen storage
capacity are essential for on-board vehicular applications.  Some reversible
complex hydrides are alanates and amides but have low reversible capacity which
is inadequate for onboard application.  High capacity, light weight, reversibility
and fast kinetics at lower temperature are the primary desirable aspects for any
type of hydrogen storage material.  Borohydride complexes as hydrogen storage
materials have recently attracted great interest.  Understanding the above
parameters for designing efficient complex borohydride materials requires
modeling across different length and time scale.  In this study, a density
functional theory study is performed to find the hydrogen storage properties
for the reversible complex borohydride material (LiNH₂)₂ -
LiBH₄ - (MgH₂) system.  The structural stability of
the reactants and products involved in the reaction steps are confirmed and
thermodynamic properties such as enthalpy of reactions and Gibbs energy are also
calculated of these reactions.  These theoretically predicted reaction steps
compare well with the experimental proposed reaction pathways.  Hydrogen storage
capacity predicted for this complex borohydride will also be presented from the
de-sorption behavior observed at different temperatures.