Modeling of molecular hydrogen and lithium adsorption on single-wall carbon nanotubes

Dubot, Pierre; Cénédèse, Pierre

doi:10.1103/physrevb.63.241402

Cited by 76 publications

(62 citation statements)

References 22 publications

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“…Theoretical investigations have focused on the intercalation of Li in SWCNTs, [23][24][25][26][27][28][29][30][31][32][33][34][35][36] in multiwall carbon nanotubes ͑MWCNTs͒, 9,21,23,37 and the calculation of energy barriers for entry and diffusion of Li inside the tubes. 24,25,27,29,30,[32][33][34][37][38][39] The binding energy of Li to nanotubes of different diameters and chiralities has been obtained in several papers 4,[23][24][25][26][27][28][29][32][33][34][35]37,38,40 using ab initio methods.…”

Section: Introductionmentioning

confidence: 99%

Interaction and concerted diffusion of lithium in a (5,5) carbon nanotube

et al. 2008

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The interaction and diffusion of lithium atoms in a (5,5) carbon nanotube is studied using density-functional theory. The Li-nanotube interaction perpendicular to the tube axis for a single Li inside and outside the tube is calculated and compared with the Li-graphene interaction obtained using the same technique. Both interactions are similar in the repulsive region but exhibit differences in their attractive part. Nevertheless, they can be described using a common parametrization. The Li-Li interaction is calculated as a function of their separation inside the tube. This interaction is similar to a screened repulsive Coulomb potential at small separations. However, at larger separations, the Li-Li interaction does not vanish and shows residual oscillations. This repulsive long-ranged interaction favors concerted diffusion of many Li atoms compared to the independent diffusion of individual Li inside the tube. The interaction and diffusion of lithium atoms in a ͑5,5͒ carbon nanotube is studied using density-functional theory. The Li-nanotube interaction perpendicular to the tube axis for a single Li inside and outside the tube is calculated and compared with the Li-graphene interaction obtained using the same technique. Both interactions are similar in the repulsive region but exhibit differences in their attractive part. Nevertheless, they can be described using a common parametrization. The Li-Li interaction is calculated as a function of their separation inside the tube. This interaction is similar to a screened repulsive Coulomb potential at small separations. However, at larger separations, the Li-Li interaction does not vanish and shows residual oscillations. This repulsive long-ranged interaction favors concerted diffusion of many Li atoms compared to the independent diffusion of individual Li inside the tube. Disciplines Engineering | Materials Science and Engineering Comments

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Section: Introductionmentioning

confidence: 99%

Interaction and concerted diffusion of lithium in a (5,5) carbon nanotube

et al. 2008

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“…PACS numbers: 61.46.+w,84.60.Ve,81.07.De Developing safe, cost-effective, and practical means of storing hydrogen is crucial for the advancement of hydrogen and fuel-cell technologies [1]. The current stateof-the-art is at an impasse in providing any material that meets a storage capacity of 6-wt% or more required for practical applications [1,2,3,4,5,6,7,8]. Here we report a first-principles computation of the interaction between hydrogen molecules and transition metal atoms adsorbed on carbon nanotubes.…”

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Titanium-Decorated Carbon Nanotubes as a Potential High-Capacity Hydrogen Storage Medium

2005

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We report a first-principles study, which demonstrates that a single Ti atom coated on a singlewalled nanotube (SWNT) binds up to four hydrogen molecules. The first H2 adsorption is dissociative with no energy barrier while other three adsorptions are molecular with significantly elongated H-H bonds. At high Ti coverage we show that a SWNT can strongly adsorb up to 8-wt% hydrogen. These results advance our fundamental understanding of dissociative adsorption of hydrogen in nanostructures and suggest new routes to better storage and catalyst materials. PACS numbers: 61.46.+w,84.60.Ve,81.07.De Developing safe, cost-effective, and practical means of storing hydrogen is crucial for the advancement of hydrogen and fuel-cell technologies [1]. The current stateof-the-art is at an impasse in providing any material that meets a storage capacity of 6-wt% or more required for practical applications [1,2,3,4,5,6,7,8]. Here we report a first-principles computation of the interaction between hydrogen molecules and transition metal atoms adsorbed on carbon nanotubes. Our results are quite remarkable and unanticipated. We found that a single Ti-atom adsorbed on a SWNT can strongly bind up to four hydrogen molecules. Such an unusual and complex bonding is generated by the concerted interaction among H, Ti, and SWNT. Remarkably, this adsorption occurs with no energy barrier. At large Ti coverage we show that a (8,0) SWNT can store hydrogen molecules up to 8-wt%, exceeding the minimum requirement of 6-wt% for practical applications. Finally, we present high temperature quantum molecular dynamics simulations showing that these systems are stable and indeed exhibit associative desorption of H 2 upon heating, another requirement for reversible storage.Recent experiments [9,10] and calculations [11,12,13,14] suggest that it is possible to coat carbon nanotubes uniformly with Ti atoms without metal segregation problems [15]. Here we show that such Ti-coated carbon nanotubes exhibit remarkable hydrogen absorption properties. Below we will present our results in detail for a (8,0) nanotube and briefly for four armchair (n,n) (n=4,5,6, and 7) and five zigzag (n,0) (n=7,8,9,10,11, and 12) nanotubes.A single Ti atom on an (8,0) SWNT has a magnetic ground state with S=1 and a binding energy of 2.2 eV; this will serve as our reference system, denoted t80Ti. In order to determine different reaction paths and products between H 2 and t80Ti, we have carried out a series of single-energy calculations as H 2 molecules approaches t80Ti and when there are large enough forces acting on H 2 molecules, we let the atoms evolve according to the quantum mechanical forces obtained from density functional theory (DFT) calculations [16]. We used the conjugated-gradient (CG) minimization and optimized both the atomic positions and the c-axis of the tube.The energy calculations were performed within the plane-wave implementation [16] −1 k-point spacing resulting in 5 k-points along the tube axis. The cutoff energy of 350 eV is found to be enough for total ...

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“…There have been a great number of reports on the search for new routes to engineer nanomaterials so that (a) they dissociate H 2 molecules into H atoms and (b) reversibly adsorb hydrogen molecules at ambient conditions 1,2,3,4,5,6,7,8,9 . Much effort has been focused on the engineering of carbon-based materials such as nanotubes 10,11 and metal hydrides such as alanates 12 .…”

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Molecular and dissociative adsorption of multiple hydrogen molecules on transition metal decoratedC60

2005

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Recently we have predicted [Phys. Rev. Lett. May 2005] that Ti-decorated carbon nanotubes can absorb up to 8-wt% hydrogen at ambient conditions. Here we show that similar phenomena occurs in light transition-metal decorated C60. While Sc and Ti prefers the hexagon (H) sites with a binding energy of 2.1 eV, V and Cr prefers double-bond (D) sites with binding energies of 1.3 and 0.8 eV, respectively. Heavier metals such as Mn, Fe, and Co do not bond on C60. Once the metals are absorbed on C60, each can bind up to four hydrogen molecules with an average binding energy of 0.3-0.5 eV/H2. At high metal-coverage, we show that a C60 can accommodate six D-site and eight H-site metals, which can reversible absorb up to 56 H2 molecules, corresponding to 7.5 wt%.PACS numbers: 61.46.+w,84.60.Ve,81.07.De An efficient storage media for hydrogen is crucial for the advancement of hydrogen and fuel-cell technologies 1 . There have been a great number of reports on the search for new routes to engineer nanomaterials so that (a) they dissociate H 2 molecules into H atoms and (b) reversibly adsorb hydrogen molecules at ambient conditions 1,2,3,4,5,6,7,8,9 . Much effort has been focused on the engineering of carbon-based materials such as nanotubes 10,11 and metal hydrides such as alanates 12 . It is found that while hydrogen-carbon interaction is too weak 10 , the metal-hydrogen interaction is too strong for hydrogen storage at ambient conditions. Very recently we have shown 13 a novel way to overcome this difficulty by forming artificial metal-carbide like structures on carbon singled-wall nanotubes (SWNT). From accurate first-principles calculations, we show that a single Ti-atom adsorbed on a SWNT can strongly bind up to four hydrogen molecules 13 . At large Ti coverage we find that a (8,0) SWNT can store hydrogen molecules up to 8-wt%, exceeding the minimum requirement of 6-wt% for practical applications. Even though these results were totally unexpected, we explained them by a simple Dewar, Chatt, and Duncanson (DCD) model 14,15 , where the interaction is due to donation of charge from the highest occupied orbital of the ligand to the metal empty states and a subsequent back donation from filled d-orbitals into the lowest unoccupied orbital of the ligand.Here we show that similar phenomena also occurs in light-transition metal decorated C 60 molecules. Below we first discuss several possible absorption sites for a single Ti atom on a C 60 molecule. We then show how a single Ti atom on a C 60 can bind up to four hydrogen molecules via Kubas interaction 14,15 . Multiple metal coverage cases, yielding up to 8 wt% hydrogen absorption, are discussed next. Finally, we briefly discuss the results for other transition metals from Sc to Co.The energy calculations were performed within the plane-wave implementation 16 of the generalized gradient approximation 17 to DFT. We used Vanderbilt ultra- soft pseudopotentials 18 treating the following electronic states as valence: Ti: 3s 2 3p 6 3d 2 4s 2 , C: 2s 2 2p 2 and H: 1s. The cutoff e...

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Modeling of molecular hydrogen and lithium adsorption on single-wall carbon nanotubes

Cited by 76 publications

References 22 publications

Interaction and concerted diffusion of lithium in a (5,5) carbon nanotube

Interaction and concerted diffusion of lithium in a (5,5) carbon nanotube

Titanium-Decorated Carbon Nanotubes as a Potential High-Capacity Hydrogen Storage Medium

Molecular and dissociative adsorption of multiple hydrogen molecules on transition metal decoratedC60

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