Hydrogen and Carbon Nanotubes

The low-temperature physisorption (type I isotherm) of hydrogen in zeolites is in good agreement with the adsorption model mentioned above for nanostructured carbon. The desorption isotherm followed the same path as the adsorption, which indicates that no pore condensation occurred. The hydrogen adsorption in zeolites depends linearly on the specific surface areas of the materials and is in very good agreement with the results on carbon nanostructures [24]. 

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S.H.S. Zein, A.R. Mohamed, Mn/Ni/Ti02 catalyst for the production of hydrogen and carbon nanotubes from methane decomposition , Energy Fuels, 18(5), 1336-1345, (2004). 

This chapter describes the storage of hydrogen in several forms of carbon, ranging from amorphous activated carbon (AC) to the ordered forms such as graphite and carbon nanotubes (CNTs). Carbon materials can be utilized for hydrogen storage in the following different ways ... 

Figure 1. Amount of hydrogen adsorbed at 298 K and 20 MPa by activated carbons (open symbols) and carbon nanotubes and nanofibres (closed symbols) versus the total micropore volume [Vpp (N )] (Figure 1(a)) and the narrow micropore volume [Vnpp (DR.CCty] (Figure 1(b)).

Z.G. Huang, Z.P. Guo, A. Calka, D. Wexler, H.K. Liu, Effect of carbon black, graphite and carbon nanotubes additives on hydrogen storage properties of magnesium, J. Alloys Compd. 427 (2007) 94-100. 

M. Rzepka, P. Lamp, M.A. de la Casa-LUlo, Physisorption of hydrogen on microporous carbon and carbon nanotubes. J. Chem. Phys. B, 102 (1998) 10894. 

The main difference between carbon nanotubes and high surface area graphite is the curvature of the graphene sheets and the cavity inside the tube. In microporous solids with capillaries which have a width not exceeding a few molecular diameters, the potential fields from opposite walls will overlap so that the attractive force which acts upon adsorbate molecules will be increased in comparison with that on a flat carbon surface [16]. This phenomenon is the main motivation for the investigation of the interaction of hydrogen with carbon nanotubes (Figure 5.14). 

S. Pekker et al., Hydrogenation of carbon nanotubes and graphite in liquid ammonia. J. Phys. Chem. B 105, 7938 (2001)... 

In recent years we are pinning our hopes on carbon nanomaterials, such as fullerenes, carbon nanofibers and carbon nanotubes for the use as hydrogen-accumulating matrixes. 

For the interaction potential between hydrogen and carbon, we introduce a new procedure to derive the Lennard-Jones parameters from existing parameters that are appropriate for carbon atoms with sp2 and sp3 hybridizations. These parameters may come from existing force fields, and may have been obtained using either experimental or ab initio results. The L-J parameters a and s are made explicitly dependent on the radius of the nanotube, r, using the following equations ... 

Gu C., Gao G. H., Yu Y. X. and Nitta T., Simulation for separation of hydrogen and carbon monoxide by adsorption on single-walled carbon nanotubes. Fluid Phase EquUibria 9A-W1 (2002) pp. 297-303. 

Several growth models are proposed for the carbon nanotubes prepared by the pyrolysis of hydrocarbons on metal surfaces. Baker and Harris [100] suggested a four-step mechanism. In the first step, the hydrocarbon decomposes on the metal surface to release hydrogen and carbon, which dissolves in the particle. The second step involves the diffusion of the carbon through the metal particle and its precipitation on the rear face to form the body of the filament. The supply of carbon onto the front face is faster than the diffusion through the bulk, causing an accumulation of carbon on the front face, which must be removed to prevent the physical... 

Volpe, M. and Cleri, F. (2003). Chemisorption of atomic hydrogen in graphite and carbon nanotubes. Surf. Sd., 544, 24-34. 

I. Cabria, M.J. Lopez and J.A. Alonso, Enhancement of hydrogen physisorption on graphene and carbon nanotubes by Li doping . The Journal of Chemical Physics, 123, 204721 (2005). 

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