Achieving High Dehydrogenation Kinetics and Reversibility of LiBH₄ by Adding Nanoporous h-BN to Destabilize LiH

Abstract

Lithium borohydride (LiBH 4 ) is a potential high-capacity hydrogen storage material but is limited by its high thermal stability and poor reversibility. Nanostructured hexagonal boron nitrides (h-BNs) with thin-layer (TL-BN) and nanoporous (NP-BN) structures have been prepared by treating h-BN in a hydrolysis process of LiBH 4 and then mixing with LiBH 4 by ball-milling to investigate their catalyzing effect on dehydrogenation and rehydrogenation. Nanostructured h-BN, in particular NP-BN, with an average pore size of 40 nm, significantly promotes the dehydrogenation kinetics, dehydrogenation capacity, and reversibility of LiBH 4 . For a LiBH 4 + NP-BN (mole ratio 1:0.3) composite, the dehydrogenation capacity reaches 13.9 wt % for LiBH 4 at 400 °C, which is very close to its theoretical one. The cycling capacity could remain stable at ∼7.6 wt % with rapid kinetics after de/rehydrogenation cycles under 10 MPa of hydrogen at 400 °C. The improved de/hydrogenation performance of LiBH 4 depends on the nanoconfinement structure of LiBH 4 in NP-BN. After dehydrogenation, a lithium-intercalated h-BN(LixBN) nanocrystal was formed by the reaction of h-BN and LiH. This LixBN nanocrystal confined the dehydrogenation products of the amorphous structure during dehydrogenation. Thus, this nanocrystal-confine-amorphous structure destabilizing LiH and benefiting the rehydrogenation and reversible capacity of the composite.

Reaction Route Optimized LiBH4 for High Reversible Capacity Hydrogen Storage by Tunable Surface-Modified AlN

“…The surface-modified AlN is prepared by an alcoholysis reaction of LiBH 4 similar to our previous work (Scheme ). , To be specific, AlN (Aladdin, 99.5% 2.0 μm) and LiBH 4 (Aladdin, 95%) were mixed well with a mass ratio of 1:1 by grinding in an agate mortar. The mixture was removed to a high-pressure reactor for treatment under 4 MPa hydrogen at 300 °C for 2 h. After cooling down to room temperature, the powder was reacted with 20 mL alcohol in a glass beaker by an ultrasonic cleaner (40 kHz, 400 W) for 1 h until no bubble formed.…”

“…In our previous work, h-BN (hexagonal boron nitride) was composited with LiBH 4. − The polarity of h-BN induces the formation of a B–H bond on the h-BN surface to destabilize LiBH 4. , Thus, higher and more stable reversible capacity is achieved due to the formation of lithium intercalation compound Li x BN between h-BN and LiH/LiBH 4.…”

“… , Thus, higher and more stable reversible capacity is achieved due to the formation of lithium intercalation compound Li x BN between h-BN and LiH/LiBH 4. Benefiting from the light element of h-BN, reversible hydrogen capacities of 3.1 and 5.7 wt % were achieved for the system of LiBH 4 -BN with mole ratios of 1:3 and 1:0.3, respectively.…”

Effects of Defective Boron Nitride Additives on Lithium-Ion Conductivity and Hydrogen-Desorption Properties of LiAlH4

“…For instance, remarkable absorption/desorption properties have been achieved in LiBH 4 /BN composites, probably because of the enhancement of H 2 dissociation, H – diffusion, and Li + diffusion by nanoscale BN . Nanostructured BN addition has a stronger effect on the kinetics than the addition of pristine h-BN. , The addition of various nitride types to the LiNH 2 /LiH composite system showed that h-BN was effective to improve hydrogen-desorption kinetics, probably because of the enhancement of Li + diffusion across the LiNH 2 /LiH interface …”

“…15 Nanostructured BN addition has a stronger effect on the kinetics than the addition of pristine h-BN. 16,17 The addition of various nitride types to the LiNH 2 / LiH composite system showed that h-BN was effective to improve hydrogen-desorption kinetics, probably because of the enhancement of Li + diffusion across the LiNH 2 /LiH interface. 18 T h i s c o n t e n t i s In our previous study, LiAlH 4 /h-BN composites were synthesized by ball-milling and their hydrogen-desorption properties were investigated.…”