ab initio study of the exo-hydrogenated single wall carbon nanotubes

Stability of the fully exo-hydrogenated zigzag (n,0) and armchair (n,n) single wall carbon nanotubes (CnHn) is studied using first-principles calculations. Zigzag and armchair carbon nanotubes (CNTs) were found to be different in electronic and atomic structures with respect to chemical hydrogenation. It was noted that the binding energy of hydrogenated carbon nanotubes revealed an approximately inverse proportionality behaviour with their diameter. Moreover, each single hydrogen atom was attached to nanotube by an exothermic process. The similar diameter exo-hydrogenated zigzag nanotubes were found to be energetically more favourable than armchair nanotubes. The calculated values of band gaps in small hydrogenated zigzag CNTs were found to be higher in both types of hydrogenated CNTs. These findings were important for particular functionalization of hydrogenated carbon nanotubes and improve the understanding to separate similar diameter zigzag and armchair nanotubes from each other through chemical functionalization.