Chemisorption and diffusion of hydrogen atoms on single-walled carbon nanotubes

Density functional theory has been performed to investigate the chemisorption and diffusion of H atoms on the surface of single-walled carbon nanotubes (SWNTs). The results show that the binding energy of a single hydrogen atom on the SWNTs surface decreases as the diameter of the tube increases and is not affected by the chirality of the tube much. Two hydrogen atoms favor binding at adjacent and opposite positions rather than at alternate carbon site. As for the diffusion of H atoms on the tube, it is found that an isolated H atom can diffuse rather than desorb on the small SWNT upon heating. As the tube diameter increases, the diffusion barrier for H atom on the surface decreases. Further study shows that when the H atom diffuses around another H atom, the diffusion barriers vary with the relative sites of the two H atoms.