Controlling the Decomposition Pathway of LiBH4 via Confinement in Highly Ordered Nanoporous Carbon

The wetting and decomposition behavior of LiBH4 has been investigated in the presence of highly ordered nanoporous hard carbon (NPC) with hexagonally packed 2 nm diameter columnar pores. Calorimetry, X-ray diffraction, and IR spectroscopy measurements confirm that the LiBH4 within the pores is amorphous. The confinement of LiBH4 in such small pores results in the disappearance of the low-temperature structural phase transition, the melting transition, and also the significant decrease of the onset desorption temperature from 460 to 220 degrees C with respect to bulk LiBH4, a lower temperature than observed in larger pore sizes in the literature. Most importantly, our results suggest that diborane release is suppressed or eliminated in the decomposition of noncrystalline LiBH4. Tight nanoconfinement may therefore mitigate both safety concerns and loss of active material in borohydride-based hydrogen storage systems.