Lithium Borohydride Nanorods: Self-Assembling Growth and Remarkable Hydrogen Cycling Properties

Nanostructured metal hydrides with unique morphology and improved hydrogen storage properties have attracted intense interests. However, the study of the growth process of highly active borohydrides remains challenging. Herein, for the first time the synthesis of LiBH₄ nanorods through a hydrogen-assisted one-pot solvothermal reaction is reported. Reaction of n-butyl lithium with triethylamine borane in n-hexane under 50 bar of H₂ at 40-100 °C gives rise to the formation of the [100]-oriented LiBH₄ nanorods with 500-800 nm in diameter, whose growth is driven by orientated attachment and ligand adsorption. The unique morphology enables the LiBH₄ nanorods to release hydrogen from ≈184 °C, 94 °C lower than the commercial sample (≈278 °C). Hydrogen release amounts to 13 wt% within 40 min at 450 °C with a stable cyclability, remarkably superior to the commercial LiBH₄ (≈9.1 wt%). More importantly, up to 180 °C reduction in the onset temperature of hydrogenation is successfully attained by the nanorod sample with respect to the commercial counterpart. The LiBH₄ nanorods show no foaming during dehydrogenation, which improves the hydrogen cycling performance. The new approach will shed light on the preparation of nanostructured metal borohydrides as advanced functional materials.