Thermodynamics and vibrational study of hydrogenated carbon nanotubes: A DFT study

Thermodynamic stability of the hydrogenated carbon nanotubes has been explored in the chemisorption limit. Statistical physics and density functional theory calculations have been used to predict hydrogen release temperatures at standard pressure in zigzag and armchair carbon nanotubes. It is found that hydrogen release temperatures decrease with increase in diameters of hydrogenated zigzag carbon nanotubes (CNTs) but opposite trend is noted in armchair CNTs at standard pressure of 1 bar. The smaller diameter hydrogenated zigzag CNTs have large values of hydrogen release temperature due to the stability of CH bonds. The vibrational density of states for hydrogenated carbon nanotubes have been calculated to confirm the CH stretching mode caused by sp3 hybridization.