Molecular Simulations of Hydrogen Storage in Carbon Nanotube Arrays

Abstract

Grand canonical ensemble Monte Carlo (GCEMC) molecular simulations of hydrogen storage at 298 and 77 K in triangular arrays of single wall carbon nanotubes (SWCNT) and in slit pores (modeling activated carbons) were performed. At 298 K the US DOE target gravimetric hydrogen storage capacity (6.5 wt %) is reached at 160 bar for optimally configured arrays of open SWCNT of wide diameter, but the equivalent volumetric capacity is ∼40% of the DOE target [695 (STP) v/v]. For slit pores at 298 K the optimal volumetric capacity is ∼20% of the target. Simulations for 77 K and 70 bar indicate that triangular arrays of open and closed SWCNT of various diameters in a wide range of configurations exceed the DOE gravimetric target. A capacity of 33 wt % is found for arrays of narrow, open, or closed SWCNT that are widely spaced.Here, adsorption occurs entirely in the interstitial space between the nanotubes. Volumetric capacities close to the DOE target are found for arrays of narrow, open or closed SWCNT with a range of interstitial spacings. The maximum volumetric capacities for simulations with slit pores at 77 K and 70 bar are ∼73% of the DOE target for a range of pore widths. Capacities from simulations for nanotubes and slit pores at 298 and 77 K are in reasonable agreement with experimentally measured capacities. It is concluded that the potential of carbon nanotubes for storage of hydrogen is superior to that of activated carbons.

Possibilities of atomic hydrogen storage by carbon nanotubes or graphite materials

“…In recent years, carbon materials such as carbon nanotubes (CNTs), carbon nanofibers and mechanically milled graphites have attracted attention owing to the availability of new carbon materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, most studies concerning the hydrogen storage have been carried out at high pressures (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and low temperatures (80-133 K) in order to store molecular hydrogen by physisorption. It has been often reported that hydrogen storage by physisorption remains less than 4 wt% at room temperature and even high pressures [1,2].…”

“…However, most studies concerning the hydrogen storage have been carried out at high pressures (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and low temperatures (80-133 K) in order to store molecular hydrogen by physisorption. It has been often reported that hydrogen storage by physisorption remains less than 4 wt% at room temperature and even high pressures [1,2]. Although large hydrogen uptakes by CNTs have been reported [3,4], these results have not been easily reproduced.…”

Enhancement of hydrogen physisorption on single-walled carbon nanotubes resulting from defects created by carbon bombardment

“…At 77 K and 70 bar, the simulation of hydrogen storage in triangular array of narrow nanotubes, which were widely separated ͑1.3 to 3.0 nm͒, showed that the DOE benchmark could be reached. 20 At 10 MPa and 77 K, the simulation of hydrogen adsorption capacity in a square lattice consisting of SWNTs of diameter ϳ2.2 nm and intertube spacing ϳ1.1 nm predicted a maximum gravimetric capacity of ϳ11.2 wt % and volumetric density of 60 Kg/ m 3 . 19 However, these very encouraging simulation results given by Refs.…”

“…[18][19][20][21] These simulations predicted that it is difficult to obtain the hydrogen storage capacity at room temperature to reach the target set by the U.S. Department of Energy ͑DOE͒ for automobile applications, i.e., the gravimetric storage of 6.5 wt % and the volumetric capacity of 62 Kg H 2 /m 3 . At 77 K and 70 bar, the simulation of hydrogen storage in triangular array of narrow nanotubes, which were widely separated ͑1.3 to 3.0 nm͒, showed that the DOE benchmark could be reached.…”

Theoretical investigation of methane adsorption onto boron nitride and carbon nanotubes

“…Several experimental and theoretical studies addressed the adsorption of methane on carbon-based nanoparticles. The focus remains on carbon nanotubes (CNTs) [10,[14][15][16] because of their unique properties including uniform porosity, high tensile strength and relative inertness. However, despite their promising results CNTs showed poor gas adsorption.…”