Synergetic Effect of in Situ Formed Nano NbH and LiH_1–xF_x for Improving Reversible Hydrogen Storage Properties of the Li–Mg–B–H System

Abstract

A significant improvement in hydrogenation/dehydrogenation properties of 2LiH/MgB 2 can be achieved by adding NbF 5 . The results show that the NbF 5 additive is effective for enhancing the de/hydrogenation kinetics of the Li−Mg−B−H system and reducing the desorption temperatures of MgH 2 and LiBH 4 . For the 2LiH− MgB 2 −0.03NbF 5 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 NbF 5 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−x F x 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.

Graphene-wrapped reversible reaction for advanced hydrogen storage

“…[5][6][7][8][9][10] A prototypical RHC is the combination of LiBH4 and MgH2 in a 2:1 molar ratio with a high theoretical hydrogen capacity of 11.4 wt.% based on Eq. (2), as well as a more advantageous dehydrogenation enthalpy (42 kJ mol -1 H 2 ) due to the formation of MgB 2 .…”

In Situ Introduction of Li3BO3 and NbH Leads to Superior Cyclic Stability and Kinetics of a LiBH4-Based Hydrogen Storage System

“…As we have not found the commercially supplied NbH and we also failed in the successful synthesis of high-purity NbH, the effect of single NbH on the hydrogen storage property of LiBH 4 is not analyzed in this study. However, in a previous report, 57 in situ formed NbH particles in a Li−Mg−B−H system were supposed to act as "active gateways", which facilitated the diffusion of hydrogen and thence improved the kinetics. Figure 10 shows the solid-state NMR spectra of the chemical shift of B nuclei of the hydrogenation products of the LiBH 4 -0.04(Li 3 BO 3 + NbH) system as well as the pristine LiBH 4 at different states.…”

“…As we have not found the commercially supplied NbH and we also failed in the successful synthesis of high-purity NbH, the effect of single NbH on the hydrogen storage property of LiBH 4 is not analyzed in this study. However, in a previous report, in situ formed NbH particles in a Li–Mg–B–H system were supposed to act as “active gateways”, which facilitated the diffusion of hydrogen and thence improved the kinetics.…”

Superior Reversible Hydrogen Storage Properties and Mechanism of LiBH4–MgH2–Al Doped with NbF5Additive

“…Recently, we have also investigated the effects of various fluoride additives (NbF 5 , TiF 3 , CeF 3 , LaF 3 , and FeF 3 ) on the de/rehydrogenation properties of 2LiBH 4 –MgH 2 , , in which NbF 5 additive shows the best performance on catalysis and cycling stability. Meanwhile, a fundamental insight into the transition and mechanism of NbF 5 has been revealed. , On the other hand, it has been reported that both doping an additive and hydrogen back pressure exhibit a combined effect on improving the dehydrogenation kinetics and suppressing the formation of Li 2 B 12 H 12 in the LiBH 4 –MgH 2 system . Herein, our present investigations are focused on the promotion of cycling stability and mechanism of the LiBH 4 –MgH 2 –Al system.…”

“…To obtain a good cycling property, hydrogen back pressure is needed for the complete formation of MgB 2 with a slow kinetics because of the incubation period . According to reaction , a reversible hydrogen capacity as high as 8–10 wt % of this Li–Mg–B–H system can be obtained. , It is an effective strategy that utilizes reactive hydride composites on the dehydrogenation reactions of LiBH 4 to obtain more stable phases such as metal borides and destabilize the borohydrides, enhancing the thermodynamic performance . In addition, more explorations have been conducted and more multiple composites have been demonstrated, such as NaAlH 4 –MgH 2 –LiBH 4 , NaAlH 4 –Mg­(BH 4 ) 2 , and 2NaBH 4 + MgH 2 systems.…”