Abstract
The influence of mechanical bending to tuning the hydrogen storage of Ni-functionalized of zigzag type of boron nitride nanotubes (BNNTs) has been investigated using density functional theory (DFT) with reference to the ultimate targets of the US Department of Energy (DOE). Single Ni atoms prefer to bind strongly at the axial bridge site of BN nanotube, and each Ni atom bound on BNNT may adsorb up to five, H2 molecules, with average adsorption energies per hydrogen molecule of )-1.622,-0.527 eV( for the undeformed B40N40-? = 0 , ) -1.62 , 0-0.308 eV( for the deformed B40N40-? = 15, ) -1.589, -0.310 eV( for the deformed B40N40-? = 30, and ) -1.368- -0.323 eV( for the deformed B40N40-? = 45 nanotubes respectively. with the H-H bonds between H2 molecules significantly elongated. The curvature attributed to the bending angle has effect on average adsorption energies per H2 molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 5.691 wt % for 5H2 Ni B40N40-? = 0, 15, 30, 45. While the desorption activation barriers of the complexes nH2 + Ni B40N40-? = 0 (n = 1-4) are outside the (DOE) domain (-0.2 to -0.6 eV), the complexes nH2 + Ni- B40N40-? = 0 (n = 5) is inside this domain. For nH2 + Ni- B40N40-? = 15, 30, 45 with (n = 1-2) are outside the (DOE) domain, the complexes nH2 + Ni- B40N40-? = 15, 30, 45 with (n = 3-5) are inside this domain. The hydrogen storage of the irreversible 4H2+ Ni- B40N40-? = 0, 2H2+ Ni- B40N40-? = 15, 30, 45 and reversible 5H2+ Ni- B40N40-? = 0, 3H2+ Ni- B40N40-? = 15, 30, 45 interactions are characterized in terms of density of states, pairwise and non-pairwise additivity, infrared, Raman, electrophilicity and molecular electrostatic potentials. Our calculations expect that 5H2- Ni- B40N40-j = 0, 15, 30, 45 complexes are promising hydrogen storage candidates.
Highlights
Carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) have attracted much attention as candidates for a hydrogen storage media [1,2]
The interaction of hydrogen molecules with material surfaces can be enhanced by heteropolar bonds at surfaces, a feature that is present in BNNTs but absent in CNTs
The main objective of the present work is to investigate the interactions between Ni and undeformed (φ = 0) and bending-deformed (φ = 15, 30,45) decorated single-walled zigzag (8,0) BNNT as well as between nH2 and Ni– undeformed and bending-deformed (8,0) BNNT in terms of several structural and energetic properties such as bond lengths, natural bond orbital (NBO) charges, density of states (DOS), adsorption energies (Eads.) and energy gaps (highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO))
Summary
Carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) have attracted much attention as candidates for a hydrogen storage media [1,2]. Boron nitride nanotubes (BNNTs) are inorganic analogues of carbon nanotubes (CNTs) [5]and possess physical properties suitable for a broad variety of applications [6]. The interaction of hydrogen molecules with material surfaces can be enhanced by heteropolar bonds at surfaces, a feature that is present in BNNTs but absent in CNTs. the interaction of hydrogen molecules with material surfaces can be enhanced by heteropolar bonds at surfaces, a feature that is present in BNNTs but absent in CNTs Given give these unique properties, as one of the most interesting non-carbon nanotubes [13], BNNT has high potential practical application in hydrogen storage
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