Clustering of functional molecules on a single-walled carbon-nanotube surface and its effect on hydrogen storage

This first-principles study deals with the effect of clustering of different functional molecules adsorbed on the surface of the single-walled carbon nanotubes (SWCNTs) (5, 5). Here we report the results of our investigation on the effect of clustering on storage capacity, the nature of H₂ bonding and strength of H₂ binding. The investigation is carried out for (5, 5) SWCNT functionalized with different types of hydrogen-rich molecules such as AlH₃,NH₃,BH₃ and NiH₂. In the case of AlH₃, the clustering turns into dimerization with the adsorption of H₂. This is distinctly different from the other three cases. Weak clustering is observed for full coverage of NH₃ molecules. The clustering starts with higher coverage of H₂ molecules in the case of SWCNT functionalized with BH₃ molecules. The clusters of NiH₂ molecules, chemisorbed on the surface of carbon nanotube, are observed. Our study indicates that depending upon the materials used for the functionalization, the clustering pattern is different and the effect on the above-mentioned factors is also different.