Theoretical study of the adsorption of H2 on (3,3) carbon nanotubes -: art. no. 045444

Using density functional theory with the generalized gradient approximation, we have studied the H-2 adsorption on (3,3) carbon nanotube with a small diameter of 4 A. Three adsorption states are found, including one physisorption and two chemisorption states. We find that a chemisorption state similar to that previously reported for larger diameter nanotube will actually evolve into a lower energy state with the underlying C-C bond ripped upon a small perturbation. An energy barrier of 2.7 eV is found for H-2 dissociation on the tube. Since the barrier is high, the dissociation of H-2 should be a rare event and the interaction of H-2 with (3,3) tube is mainly through physisorption. But once chemisorption occurs, the hydrogenated tube is only metastable against ripping.