Mo2N-Activated Metal Borohydride Nanocomposites for H2 Storage

Metal hydrides play a pivotal role in advancing the hydrogen economy by providing a compact solution for onboard hydrogen storage. However, their practical application is hindered by undesirable side reactions and slow kinetics during hydrogen uptake and release. We present herein enhanced thermodynamics and kinetics of hydrogen uptake/release through the infiltration of lithium borohydride (LiBH₄) into Mo₂N-doped defective boron nitride (Mo₂N-DBN) host. Density functional theory (DFT), Ab initio molecular dynamics (MD), and a wide array of experimental data suggested that the Mo₂N-DBN host promotes proximity between the active sites of LiBH₄, effectively preventing aggregation during sorption processes, thereby leading to a reversible hydrogen storage capacity of 10.80 wt % at 200 °C and 50 bar for LiBH₄@Mo₂N-DBN composite with minimal loss after five hydrogenation-dehydrogenation cycles. This marked an 84% enhancement over pure LiBH₄ under identical conditions and represented the highest reported storage capacity among LiBH₄-based composites to date. The Mo₂N sites in the composite prevented direct melting transitions of LiBH₄ and facilitated the weakening of H–H bonds, which in turn gave rise to fast dehydrogenation kinetics (E_a = 77.44 ± 0.02 kJ/mol). Additionally, analysis of hydrogenation-dehydrogenation energetics indicated that Li atoms are drawn from the LiBH₄ cluster toward Mo₂N sites, coordinating with N atoms and thereby promoting better interface stability. We anticipate the continuous formation of interfaces between Mo₂N-DBN, LiH, and B, where rehydrogenation reactions can proceed efficiently, supported by the migration of H-containing species between bulk and interfacial regions.