Interaction of hydrogen molecules on Ni-doped single-walled carbon nanotube

Adsorption of hydrogen molecules on an Ni-doped (8,0) single-walled carbon nanotube (SWNT) is investigated by using first-principles density functional calculations. The result shows that a single Ni atom adsorbed on the bridge site of the tube could cannot dissociate the H₂, however it can chemisorb three H₂ at most, with the average binding energy per H₂ suitable for the hydrogen storage at the room temperature. More H₂ would physisorb around an Ni atom weakly. As for the SWNT with an Ni dimer adsorbed, we find that when the H₂ approaches the Ni--Ni bond, it dissociates without overcoming any barrier and makes bonds with Ni atom.