Hydrogen adsorption and cohesive energy of single-walled carbon nanotubes

Abstract

Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes ͑SWNT͒ was found to exceed 8 wt. %, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occurs where there is a separation of the individual SWNTs, and hydrogen is physisorbed on their exposed surfaces. The pressure of this phase transition provides a tube-tube cohesive energy for much of the material of 5 meV/C atom. This small cohesive energy is affected strongly by the quality of crystalline order in the ropes.

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

“…3. This result is consistent with many experiments, which reported that SWNTs have a certain hydrogen storage capacity at low temperature, [13][14][15] but have very low hydrogen uptake capacity at room temperature. [8][9][10][11][12] For H 2 molecules adsorbed on defected SWNTs, the situation is very different.…”

“…2. The collision energy, 0.01 eV, is equivalent to the average translational kinetic energy of a particle system at a thermal equilibrium temperature of ϳ77 K. The high sticking coefficient in this case is consistent with the experimental results, [13][14][15][16] which showed that hydrogen uptake under cryogenic operating conditions were more favorable than at an ambient temperature. The second feature shown in Fig.…”

“…[8][9][10][11][12] Hydrogen storage in carbon nanotubes at low temperature and high pressure may be more suitable for obtaining higher hydrogen storage capacity. Hydrogen adsorption capacity more than 8 wt % in purified crystalline ropes of SWNTs was observed at ϳ128 atm and at 80 K. 13 A storage capacity of more than 6 wt % at T = 77 K and pressure 1 -2 atm for hydrogen physisorbed on heavily processed ropes of SWNTs was also reported. 14,15 Open tipped MWNTs were found to adsorb about 6.46 wt % of hydrogen at 77 K and at a pressure of ϳ12 MPa.…”

Advances in the application of nanotechnology in enabling a ‘hydrogen economy’

“…Ye et al [175] reported a storage capacity of 8 wt.% for purified SWNTs at 80 K and a hydrogen pressure of 130 bar. SWNTs were purified by sonicating for 10 h in dimethyl formide followed by vacuum degassing for 10 h at 220°C.…”

Diagnostics of laser-produced plume under carbon nanotube growth conditions

“…During recent years, there has been a tremendous increase in interest in the production and characterization of carbon nanotubes, due to their unique mechanical and electrical properties leading to potential applications in nanoelectronics [1,2], nanostructures [3,4] and energy storage [5,6]. from the transition d31-lg-a3I-lu.…”