Prediction of a multicenter-bonded solid boron hydride for hydrogen storage

Abstract

A layered solid boron hydride structure (B${}_{2}$H${}_{2}$) consisting of a hexagonal boron network and bridge hydrogen which has a gravimetric capacity of $8\mathrm{wt}\mathrm{%}$ hydrogen is predicted. The structural, electronic, and dynamical properties of the proposed structure are investigated using first-principles electronic structure methods. The absence of soft phonon modes confirms the dynamical stability of the proposed structure. Charging the structure significantly softens hydrogen related phonon modes. Boron modes, in contrast, are either hardened or not significantly affected by electron doping. Furthermore, self-doping the structure considerably reduces the energy barrier against hydrogen release. These results suggest that electrochemical charging or self-doping mechanisms may facilitate hydrogen release while the underlying boron network remains intact for subsequent rehydrogenation.