Grand canonical Monte Carlo simulation of isotherm for hydrogen adsorption on nanoporous LiBH4

Abstract

Light metal borohydrides and especially lithium borohydride (LiBH4) has attracted a great deal of attention in recent years because of its large gravimetric and volumetric hydrogen density. However, LiBH4 is thermodynamically too stable for the hydrogenation/dehydrogenation cycles to proceed at practical pressure and temperature. In this work, we offer a new route to use LiBH4 as hydrogen storage material that various nanopores within LiBH4 crystal are constructed for physisorbing molecular hydrogen. The interaction between a single H2 molecule and the nanoporous LiBH4 is proposed by density functional theory (DFT). Calculating adsorption isotherms and isosteric heats of adsorption of H2 in designing new sorbents using grand canonical Monte Carlo (GCMC) simulations are performed at 298 and 77K, in a broad range of 0.1–100bar. It is identified that the porosity of the material considered has a strong impact on the adsorption capacity. At room temperature, values of hydrogen adsorption capacities of a maximum of 1.35wt.% in gravimetric, 4.70g/L of volumetric have been obtained at 100bar, respectively. At 77K, the absolute hydrogen storage capacity in the best structure considered is 9.36wt.% and 35.41g/L at 100bar as well as the excess hydrogen storage of 5.87wt.% and 21.39g/L at 40bar, respectively. These results may be used to provide a new route for using LiBH4 as a hydrogen storage medium.