Synergetic Effect of in Situ Formed Nano NbH and LiH_1–<i>x</i>F_<i>x</i> for Improving Reversible Hydrogen Storage Properties of the Li–Mg–B–H System

A significant improvement in hydrogenation/dehydrogenation properties of 2LiH/MgB₂ can be achieved by adding NbF₅. The results show that the NbF₅ additive is effective for enhancing the de/hydrogenation kinetics of the Li–Mg–B–H system and reducing the desorption temperatures of MgH₂ and LiBH₄. For the 2LiH–MgB₂–0.03NbF₅ sample, About 9.0 wt % hydrogen capacity is obtained rapidly under cyclic conditions of rehydrogenation within 20 min at 350 °C and dehydrogenation within 20 min at 400 °C; thus, catalytic improvement persists well in the subsequent reversible dehydrogenation cycles. Moreover, the sample could reversibly reabsorb and release more than 9.0 wt % hydrogen even at 250 and 375 °C, respectively. Microstructure analyses reveal that the NbF₅ additive in improving the de/hydrogenation properties of Li–Mg–B–H system could be ascribed to the synergistic effect of in situ formed nano NbH particles acting as “active gateways” facilitating the diffusion of hydrogen, and the “favorable thermodynamic destabilization” from the reversible transition of LiH_1–<i>x</i>F_<i>x</i> caused by functionality of F-anion substitution. This fundamental understanding provides us with insights into the design and optimization of the catalytic method and species for the catalyzed Li–Mg–B–H system