Hydrogen Sorption on the Different Types of the Boron-Carbon Nanotubes (original) (raw)
Related papers
2020
In this research interaction of atomic and molecular hydrogen with carbon nanotubes containing boron impurities is considered. Process was modelled by step-by-step approach of atom or molecule of hydrogen to a surface of a nanotube. Calculations were carried out with use of model of a molecular cluster within a method of density functional theory (DFT). The research of the electronic and energy structure of the complex received in a consequence of influence of step-by-step approach of adatom to a surface of a carbon nanotubes containing boron impurities was conducted.
E-Journal of Chemistry, 2011
The density functional theory (DFT) has been used to simultaneously investigate physic/chemi-sorption properties of oxygen on the (5, 5) boron nitride nanotube (BNNT). Geometry optimizations were carried out at B3LYP/6-31G*level of theory using gaussian 98 suites of program. physisorption of O2outside the BNNT with a vertical orientation to the tube axis above a boron atom is the most stable state of physisorption and its binding energy is -0.775 kcal/mol. In the chemisorption of O2molecule, the most stable state is above two adjacent B and N atoms of a hexagon with a B-N bond length of 2.503 Å and the binding energy of adsorbed oxygen atoms -14.389 kcal/mol. Based on these results, We also provide the effects of O2adsorption on the electronic properties of BNNTs.
Ab initiostudy of hydrogen interaction with pure and nitrogen-doped carbon nanotubes
Physical Review B, 2007
Detailed studies of mechanisms for hydrogen dissociative adsorption and diffusion on pure and nitrogendoped ͑8, 0͒ carbon nanotubes are carried out using the first-principles density functional theory method. ͑1͒ For pure carbon nanotubes, we have identified the energetically most favorable dissociative pathway for hydrogen adsorption, with a barrier height of 1.3 eV. We also found that the adsorbed hydrogen atoms can act as an autocatalyst for further dissociative adsorption of hydrogen molecules. ͑2͒ It is found that on pure carbon nanotubes the diffusion of hydrogen atoms is constrained by interaction with neighboring adsorbed hydrogen atoms. The diffusion barrier is around 0.7 eV for an isolated hydrogen atom, but becomes substantially higher at around 1.4 eV in the presence of adsorbed hydrogen in neighboring positions. ͑3͒ Doping the nanotube with nitrogen considerably alters the catalytic effects of the carbon nanotube for hydrogen dissociative adsorption. The dissociative adsorption of hydrogen on the carbon nanotube is greatly enhanced, with the barrier substantially reduced to ca. 0.9 eV. The differences in the barrier heights are explained through analysis of the electronic structure changes of the nanotube.
The present experimental study reports on hydrogen desorption behavior of hydrogenated single-walled carbon nan- otubes (SWCNTs), functionalized with borane (BH 3 ). Desorption is carried out using a thermal annealing technique. The hydro- genated samples are annealed at 200 ◦ C for 30 min and character- ized using Fourier transform infrared (FTIR) and Raman spec- troscopy studies. The amount of released hydrogen is measured by thermogravimetric/thermal desorption spectroscopy (TG/TDS) studies. FTIR and Raman studies confirm the desorption of hy- drogen. The TG/TDS results reveal that 100% of stored hydrogen is released in approximately 1.5 min in the temperature range 100–150 ◦ C
Hydrogen sorption by carbon nanotubes and other carbon nanostructures
Journal of Alloys and Compounds, 2002
We have analyzed the hydrogen storage capability of a set of carbon samples including a variety of carbon nanotubes, in the gas phase and in the electrolyte as well. The nanotube samples synthesized in our laboratory by pyrolysis of acetylene are of the multi-wall type. The hydrogen sorption properties of our synthesized nanotubes were compared with the properties of commercially available nanotubes and high surface area graphite as well. The nanotube samples and the high surface area graphite as well absorb hydrogen up to 5.5 mass% at cryogenic temperatures (77 K). However, at room temperatures this value drops to¯0.6 mass%. The electrochemical experiments on the carbon samples showed a maximum discharge capacity of 2.0 mass% at room temperature (298 K). The hydrogen tends to covalently bind to carbon when the absorption takes place at elevated temperatures (.573 K). Therefore, hydrocarbons desorbed from the sample were analyzed by means of temperature programmed desorption measurements. We conclude that the adsorption of hydrogen on nanotubes is a surface phenomenon and is similar to the adsorption of hydrogen on high surface area graphite.
Adsorption, 2018
The hydrogen adsorption capabilities of Titanium functionalized single-walled BN nanotubes (BNNTs) with B-N defects was assessed by density-functional theory tight binding (DFTB) method. According to the DFTB molecular dynamics simulations, the BNNT structures were thermodynamically stable, the Ti atom once incorporated with the B-N defects present in BNNT (Ti-BNNT) protrudes to the external surface of the BNNT sidewall. The titanium atoms does not agglomerate to form any metal clusters. The results revealed that at 77 K and 10,000 KPa, the H 2-Ti-BNNT has a gravimetric hydrogen storage capacity above 7 wt% ideal for department of energy specifications. Further calculations suggest that the Ti-BNNT has a good affinity towards H 2 molecules and under low pressure of 500 KPa. The H 2 stays close to the Ti metal due to its partially cationic character with some H 2 attaching itself at the BNNT surface due to heteropolar bonding. H 2 atoms is physisorbed in analogous to or resembling something molecular near the Ti sites which gives rise to a significant storage capacity for H 2 in these modified BNNT.
Hydrogen storage in boron substituted carbon nanotubes
Carbon, 2007
Template assisted synthesis of boron substituted carbon nanotubes was carried out by the carbonization of hydroborane polymer in alumina membrane template. The nanotubes were characterized by electron microscopic analysis, FT-Raman, FT-IR, XRD, X-ray photoelectron spectroscopy (XPS) and 13 C & 11 B MAS NMR techniques. The presence of boron in different chemical environment has been visualized by XPS and 11 B MAS NMR. The hydrogen absorption activity has been studied and a maximum of 2 wt% hydrogen storage capacity was observed.
Adsorption Science & Technology, 2013
Changes in the structural and electronic properties of chemically modified boron nitride nanotubes (BNNTs) using methanol and its derivatives including CH 3 CH 2 CH 2 OH , CH 3 CH 2 OH, (ph)CH 2 CH 2 OH, CH 2 COOH and (CN)CH 2 CH 2 OH were investigated using density functional theory calculations. The study results showed that molecules of methanol can be chemically adsorbed on top of a sidewall B atom with an adsorption energy of −0.67 eV, which is stronger than that of carbon nanotubes. When using different derivatives of methanol, the adsorption energies and charge transfer from the adsorbate to the BNNT depending on the electron-withdrawing or electrondonating capability of the subgroups within the derivatives. Subgroups with strong electron-withdrawing capability generally lead to transfer less charge and smaller adsorption energy. The calculated density of state shows that the electronic properties of the BNNT are only slightly changed by the chemical modification. However, preservation of the electronic properties of BNNTs coupled with the enhanced solubility suggests that chemical modification of BNNTs with either methanol or its derivatives may be an effective way for purification of the BNNTs.
Retracted: Computational study of hydrogen adsorption on potassium-decorated boron nitride nanotubes
International Nano Letters
We have investigated the potassium-decorated boron nitride nanotubes for hydrogen storage using semi-empirical AM1 method. The ultra narrow (3,3) and (5,0) boron nitride nanotubes of same diameter but of different chirality have been used. Both of them show hydrogen storage greater than 8 % by weight. Density of states have been calculated, and it is found that the presence of alpha density of state of potassium results in smaller energy gap; as a result of which, the conductivity of the potassium-decorated boron nitride nanotubes is enhanced as compared to pristine boron nitride nanotubes. Charge decomposition analysis showed that there is significant transfer of charge from adsorbate potassium to boron nitride nanotubes; the same is also confirmed by Mulliken population analysis. For same diameter, due to different electronic configuration, zigzag tube is found to be slightly more favorable for hydrogen adsorption. The results of the present simulation study suggest that the potassiumdecorated boron nitride nanotubes are good candidate for hydrogen adsorption.