Computational Investigation of Hydrogen Storage Capacity of Boron Nitride Nanocages by Newly Developed PM7 Method (original) (raw)
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International Journal of Hydrogen Energy, 2009
We use ab initio density functional theory calculations to study the interaction of hydrogen with vacancies in boron nitride nanotubes to optimize the hydrogen storage capacity through defect engineering. The vacancies reconstruct by forming B-B and N-N bonds across the defect site, which are not as favorable as heteronuclear B-N bonds. Our total energy and structure optimization results indicate that the hydrogen cleaves these reconstructing bonds to form more stable atomic structures. The hydrogenated defects offer smaller charge densities that allow hydrogen molecule to pass through the nanotube wall for storing hydrogen inside the nanotubes. Our optimum reaction pathway search revealed that hydrogen molecules could indeed go through a hydrogenated defect site with relatively small energy barriers compared to the pristine nanotube wall. The calculated activation energies for different diameters suggest a preferential diameter range for optimum hydrogen storage in defective boron nitride nanotubes. ª
Science of Advanced Materials, 2013
In the quest for promising hydrogen storage materials, we have performed first principles calculations on CLi 3 and OLi 2 decorated hexagonal boron nitride (h-BN), sheet. The strong binding of the polylithiated species to pristine and doped BN sheet and the large distance between these functionalized species ensure their uniform distribution over the sheet without being clustered. MD simulations have also confirmed the stabilities of both functionalized systems. Bader analysis and density of states reveals the bonding nature in the systems. A reasonably high H 2 storage capacity with the adsorption energies within the desired window suggests that these systems hold promise as efficient H 2 storage mediums.
Hydrogen Storage in Bilayer Hexagonal Boron Nitride: A First-Principles Study
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Preparation and electrochemical hydrogen storage of boron nitride nanotubes
Boron nitride (BN) nanotubes were synthesized through chemical vapor deposition over a wafer made by a LaNi 5 /B mixture and nickel powder at 1473 K. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were performed to characterize the microstructure and composition of BN nanotubes. It was found that the obtained BN nanotubes were straight with a diameter of 30-50 nm and a length of up to several microns. We first verify that the BN nanotubes can storage hydrogen by means of an electrochemical method, though its capacity is low at present. The hydrogen desorption of nonelectrochemical recombination in cyclic voltammograms, which is considered as the slow reaction at BN nanotubes, suggests the possible existence of strong chemisorption of hydrogen, and it may lead to the lower discharge capacity of BN nanotubes. It is tentatively concluded that the improvement of the electrocatalytic activity by surface modification with metal or alloy would enhance the electrochemical hydrogen storage capacity of BN nanotubes.
International Journal of Hydrogen Energy, 2017
In this study, hydrogen storage properties of the B 24 N 24 and Al 24 N 24 nanocages have been computationally investigated by the DFT method whose suitability was determined with a thorough methodological analysis. This analysis includes comparison of the performances of a number of DFT functionals against the CCSD(T) method for the determination of the best DFT method that is able to accurately model H 2-BN and H 2-AlN systems. The ɷB97X-D, B3LYP-D2, PBEPBE-D2, BHandH methods produced results close to that of the reference CCSD(T) method. Of all methods studied, ɷB97X-D, showing the best performance, is found to be the most appropriate DFT method for H 2-B 24 N 24 and Al 24 N 24 systems including dispersive interactions between hydrogen and the host molecule. The ɷB97X-D calculations result in that H 2 molecule make the tightest adsorptive bond with Al atom in Al 24 N 24 having an adsorption energy of À0.116 eV, by forming much more stable complex than the H 2-B 24 N 24 one. This indicates that Al 24 N 24 has better exohedral hydrogen storage properties. The calculations also revealed that H 2 molecules cannot pass through hexagonal rings of B 24 N 24 instead they chemisorb on the cage atoms by breaking BN bond while they can pass through hexagonal rings of Al 24 N 24 without making any damage in the AleN bond, leading the fact that the AleN bond is stronger than the BeN bond. Moreover, endohedral addition of H 2 molecules up to three can form thermodynamically stable nH 2 @Al 24 N 24 complexes while endohedral hydrogen addition to B 24 N 24 destabilizes the complexes. Thus, the Al 24 N 24 nanocage is not only structurally more stable than B 24 N 24 nanocage, but also it can accommodate more hydrogen molecules, so it is better candidate for both endohedrally and exohedrally hydrogen storage compared to B 24 N 24 .
Ceramics International, 2017
Top-down approach has been used to synthesize pure, highly crystalline, multilayered micron size crystals of hexagonal boron nitride (BNMCs) at the top of Silicon substrate at 800°C by using bulk boron nitride powder as a precursor. The synthesized crystals have different interlayers spacing from left to right (0.33 nm, 0.37 nm and 0.35 nm) and at the center (~0.24 nm). The former spacing corresponds to d (002) spacing whereas the later corresponds to d (010) spacing in h-BN. The sharpness of the peaks in XRD, Raman and FTIR spectrums correspond to highly crystalline nature of BNMCs whereas the locations of the peaks verify the h-BN nature of BNMCs. The B-N bonded BNMCs with larger surface area can be an excellent choice as a hydrogen storage element.
Industrial & Engineering Chemistry Research
Boron nitride nanotubes (BNNT) were synthesized over both Fe3+ impregnated MCM-41 (mobil composition of matter no. 41) and Fe2O3/MCM-41 complex catalyst systems at relatively low temperatures for 1 h by the chemical vapor deposition technique in large quantities. The formation of BNNT was tailored at different reaction temperatures by changing catalyst type. The use of Fe3+-MCM-41 and Fe2O3 as a complex catalyst system led to thin and thick tube formations. The diameters of BNNTs were in the range of 2.5–4.0 nm for thin tubes and 20–60 nm for thick tubes. The thin tube formation originated from the growth of BNNT over Fe3+-MCM-41 due to its average pore size of 4 nm. Higher reaction temperatures caused both BNNT and iron-based side product formations. The hydrogen uptake capacity measurements by the Intelligent Gravimetric Analyzer at room temperature showed that BNNTs could adsorb 0.85 wt % hydrogen which was two times larger than that for commercial carbon nanotubes.
The basic need for the survival and growth of living beings in this planet is energy. An uncontrolled usage of the fossil fuels in the various industrial sectors particularly in automobile industry has created panic regarding its availability in future. Dearth of fossil fuel reserves is alarming, as these underground resources are the prime reserves of energy other than the sun. The earth has been suffering from the dual curses of the greenhouse effect, caused due to environmental pollution, as well as shortage of fossil fuel reserves, caused due to excessive use of energy. Under these circumstances for the well-being of human beings scientists have being doing a lot of research on finding alternative sources of energy other than the natural fossil fuel reserves is of high importance. The use of hydrogen as an alternative source of energy is quiet important in this regard. Hydrogen is the third most abundant element on the earth , s surface, found everywhere -on the rocks, soils, air and obviously in water. Hydrogen demonstrates itself as one of the simplest chemical systems and upon combustion produces water as a harmless byproduct. Hydrogen has thus been conceived as a clean fuel source as against the oil and natural gas resources and unlike the latter, seldom pollutes the environment. Moreover, hydrogen has the highest energy density per kilogram in comparison with other combustible fuels, particularly natural gas. However, the use of hydrogen as a fuel source depends on its effective and safe means of storage. Hydrogen is extremely reactive in nature and therefore is not easy to control. It readily participates in combustion process. BN fullerene materials would store H 2 molecule easier than carbon fullerene materials, and its stability for high temperature would be good. The purpose of the present work is to investigate hydrogen gas storage and adsorption it on the BN nanocluster i.e. B 16 N 16 and B 24 N 24 , K + @B 16 N 16 and K + @B 24 N 24 by DFT/ M062X/6-311G (D, P) with Gaussian 09 software. We have calculated the HOMO-LUMO and Band gap and adsorption energy, Dipole moments and charge transfers. In the next stage we compare two these groups from the point view of adsorption energy. According to this work , it can be seen by placing K + within B 16 N 16 and B 24 N 24 nanofullerenes like structures , the adsorption energy is much than to the case where the K + cation is not. We have find the highest dipole moment and absorbed energy for H 2 /K + @B 16 N 16 among them. 2