The defect effect upon H adsorption on single-walled C nanotubes was studied by using extensive molecular dynamics simulations and density functional theory calculations. It indicated that the defects created on the exterior wall of the single-walled C nanotubes by bombarding the tube wall with C atoms and C2 dimers at a collision energy of 20eV could enhance the H adsorption potential of the single-walled C nanotubes substantially. The average adsorption energy for a H2 molecule adsorbed on the exterior wall of a defected (10,10) single-walled C nanotubes was ~150meV, while that for a H2 molecule adsorbed on the exterior wall of a perfect (10,10) single-walled C nanotubes was ~104meV. The H2 sticking coefficient was very sensitive to temperature, and had a maximum value around 70 to 90K. The electron density contours, the local density of states, and the electron transfers obtained from the density functional theory calculations clearly indicated that the H2 molecules were all physisorbed on the single-walled C nanotubes. At above 200K, most of the H2 molecules adsorbed on the perfect single-walled C nanotubes were soon desorbed, but the H2 molecules could still remained on the defected single-walled C nanotubes at 300K. The detailed processes of H2 molecules adsorbing on and desorbing from the (10,10) single-walled C nanotubes were demonstrated.

Enhancement of Hydrogen Physisorption on Single-Walled Carbon Nanotubes Resulting from Defects Created by Carbon Bombardment. Y.Xia, J.Z.Zhu, M.Zhao, F.Li, B.Huang, Y.Ji, X.Liu, Z.Tan, C.Song, Y.Yin: Physical Review B, 2005, 71[7], 075412 (8pp)