Direct synthesis of Li[BH4] and Li[BD4] from the elements

The direct synthesis of Li[BH4] and Li[B11D4] from the corresponding elements at T = 700 °C and p(H2) (or p(D2)) = 150 bar is demonstrated. The chemical inertness of boron is thought to prevent its reaction with lithium and hydrogen to LiBH4 at lower temperatures. We show, however, that the reaction kinetics can be enforced by a LiB3-like alloy and a Li7B6 intermetallic compound, which are formed in inert argon atmosphere at 330 and 450 °C, respectively. The synthesis is performed by exposing the Li–B mixtures to a defined hydrogen pressure in a high pressure stainless steel vessel and the hydrogen adsorption is monitored by the pressure decrease. The product is identified by X-ray powder diffraction.