A Unique Double-Layered Carbon Nanobowl-Confined Lithium Borohydride for Highly Reversible Hydrogen Storage

Poor reversibility and high desorption temperature restricts the practical use of lithium borohydride (LiBH₄ ) as an advanced hydrogen store. Herein, a LiBH₄ composite confined in unique double-layered carbon nanobowls prepared by a facile melt infiltration process is demonstrated, thanks to powerful capillary effect under 100 bar of H₂ pressure. The gradual formation of double-layered carbon nanobowls is witnessed by transmission electron microscopy (TEM) observation. Benefiting from the nanoconfinement effect and catalytic function of carbon, this composite releases hydrogen from 225 °C and peaks at 353 °C, with a hydrogen release amount up to 10.9 wt%. The peak temperature of dehydriding is lowered by 112 °C compared with bulk LiBH₄ . More importantly, the composite readily desorbs and absorbs ≈8.5 wt% of H₂ at 300 °C and 100 bar H₂ , showing a significant reversibility of hydrogen storage. Such a high reversible capacity has not ever been observed under the identical conditions. The usable volumetric energy density reaches as high as 82.4 g L^-1 with considerable dehydriding kinetics. The findings provide insights in the design and development of nanosized complex hydrides for on-board applications.