Improvement of the hydrogen storage performance of t-graphene-like two-dimensional boron nitride upon selected lithium decoration

In recent years, search for applicable bidimensional (2D) hydrogen storage materials with high capacity and excellent H₂ physisorption properties has attracted considerable attention from scientists and researchers. According to the rational design, and using first-principles calculations, we propose a t-graphene-like boron nitride monolayer (t-B₄N₄) for hydrogen storage application by replacing C atoms in t-graphene with B and N atoms. The thermal stability and polarization mechanisms of lithium atoms adsorbed at the center of octagons on the t-B₄N₄ system were evaluated at 300 K using ab initio molecular dynamics (AIMD) calculations. Moreover, Li-decorated double-sided t-B₄N₄ can store up to 32H₂ molecules with an average hydrogen adsorption energy of 0.217 eV per H₂ and a maximum hydrogen storage capacity of 12.47 wt%. The reversibility of adsorbed hydrogen was checked and the calculated desorption temperature was 161 K, much higher than the critical point for hydrogen. Based on diffusion barriers, the H₂ molecule diffusion kinetics is faster on the t-B₄N₄ surface than that on t-graphene and graphene.

Enhanced H2 Storage Capacity of Bilayer Hexagonal Boron Nitride (h-BN) Incorporating van der Waals Interaction under an Applied External Electric Field

Lightweight two-dimensional materials are being studied for hydrogen storage applications due to their large surface area. The characteristics of hydrogen adsorption on the h-BN bilayer under the applied electric field were investigated. The overall storage capacity of the bilayer is 6.7 wt % from our theoretical calculation with E _ads of 0.223 eV/H₂. The desorption temperature to remove the adsorbed H₂ molecules from the surface of the h-BN bilayer system in the absence of an external electric field is found to be ∼176 K. With the introduction of an external electric field, the E _ads lies in the range of 0.223-0.846 eV/H₂ and the desorption temperature is from 176 to 668 K. Our results show that the external electric field enhances the average adsorption energy as well as the desorption temperature and thus makes the h-BN bilayer a promising candidate for hydrogen storage.

Capacity enhancement of polylithiated functionalized boron nitride nanotubes: an efficient hydrogen storage medium

By using first principles density functional theory simulations, we report detailed geometries, electronic structures and hydrogen (H₂) storage properties of boron nitride nanotubes (BNNTs) doped with selective polylithiated molecules (CLi₂). We find that unsaturated bonding of Li-1s states with BNNT significantly enhances the system stability and hinders the Li-Li clustering effect, which can be detrimental for reversible H₂ storage. The H₂ adsorption mechanism is explained on the basis of polarization caused by the cationic Li⁺ of CLi₂ molecules bonded with BNNT. The incident H₂ molecules are adsorbed with BNNT-nCLi₂ through electrostatic and van der Waals interactions. We find that with a maximum of 5.0% of CLi₂ coverage on BNNT, an H₂ gravimetric density of up to 4.41 wt% can be achieved with adsorption energies in the range of -0.33 eV per H₂, which is suitable for ambient condition H₂ storage applications.

Light metal decorated graphdiyne nanosheets for reversible hydrogen storage

The sensitive nature of molecular hydrogen (H₂) interaction with the surfaces of pristine and functionalized nanostructures, especially two-dimensional materials, has been a subject of debate for a while now. An accurate approximation of the H₂ adsorption mechanism has vital significance for fields such as H₂ storage applications. Owing to the importance of this issue, we have performed a comprehensive density functional theory (DFT) study by means of several different approximations to investigate the structural, electronic, charge transfer and energy storage properties of pristine and functionalized graphdiyne (GDY) nanosheets. The dopants considered here include the light metals Li, Na, K, Ca, Sc and Ti, which have a uniform distribution over GDY even at high doping concentration due to their strong binding and charge transfer mechanism. Upon 11% of metal functionalization, GDY changes into a metallic state from being a small band-gap semiconductor. Such situations turn the dopants to a partial positive state, which is favorable for adsorption of H₂ molecules. The adsorption mechanism of H₂ on GDY has been studied and compared by different methods like generalized gradient approximation, van der Waals density functional and DFT-D3 functionals. It has been established that each functionalized system anchors multiple H₂ molecules with adsorption energies that fall into a suitable range regardless of the functional used for approximations. A significantly high H₂ storage capacity would guarantee that light metal-doped GDY nanosheets could serve as efficient and reversible H₂ storage materials.

Insights into the electronic properties and reactivity of graphene-like BC3 supported metal catalysts

Graphene-like BC₃ monolayer is a new two-dimensional nanomaterial with many unique properties, but is still largely unknown.

Hydrogen storage in bimetallic Ti–Al sub-nanoclusters supported on graphene

Variations in the hydrogen gravimetric content of Ti and TiAl_n clusters supported on graphene layers.