  An ideal material for on-board hydrogen storage must release hydrogen at
practical temperature and pressure and also regenerate efficiently under
similarly gentle conditions. Therefore, thermodynamically, the hydride material
must lie within a narrow range near the hydrogenation/dehydrogenation phase
boundary. Materials involving only conventional bonding mechanisms are unlikely
to meet these requirements. In contrast, materials containing certain
frustrated bonding are designed to be on the verge of frustration-induced phase
transition, and they may be better suited for hydrogen storage. Here we propose
a novel layered solid boron hydride and show its potential for hydrogen
storage. The absence of soft phonon modes confirms the dynamical stability of
the structure. Charging the structure significantly softens hydrogen-related
phonon modes. Boron-related phonons, in contrast, are either hardened or not
significantly affected by electron doping. These results suggest that
electrochemical charging may facilitate hydrogen release while the underlying
boron network remains intact for subsequent rehydrogenation.
