Synergetic Effect of in Situ Formed Nano NbH and LiH1-xFx 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-MgB2-0.03NbF(5) sample, About 9.0 wt % hydrogen capacity is obtained rapidly under cyclic conditions of rehydrogenation within 20 min at 350 degrees C and dehydrogenation within 20 min at 400 degrees 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 degrees 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 LiH1-xFx 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.