Room-temperature hydrogen storage of boron nanoclusters

Lithium borohydride (LiBH₄) is a promising hydrogen carrier owing to its high hydrogen storage capacity. However, the low reactivity of its dehydrogenation products, boron and LiH, towards dihydrogen molecules makes the re-generation of borohydrides extremely challenging. Here we theoretically unravel that the dissociation of H₂ into H atoms and its adsorption by the active B_spike atoms (surface-protruding boron atoms with low coordination and high reactivity) is a prerequisite for the formation of B-H bond, rather than the direct reaction between H₂ and B. Moreover, the proportion of B_spike atoms increases exponentially as the size of B clusters decreases, indicating that reducing B particle size to the ultrasmall scale is critical for enhancing hydrogenation reactivity. Thereby, we experimentally synthesize nanocomposites consisting of ultrafine LiBH₄ nanoparticles decorated with 3 nm Ni catalytic clusters for hydrogen storage. Upon dehydrogenation, these nanocomposites form B and LiH clusters in close proximity at 5-10 nm scale, while the Ni clusters remain intact. The Ni clusters not only facilitate the dissociation of H₂ into H atoms but also strongly interact with the B clusters, weakening B-B bond, which enables the hydrogenation of B/LiH back to LiBH₄ at temperatures as low as 30 °C under 100 bar H₂.