(347f) Interaction of Hydrogen Molecules with Defective Graphene Sheets: An Ab Initio Study

Hydrogen appears as one of the most promising energy carriers. Hydrogen has the advantage of being the cleanest fuel and as a result it can efficiently help limiting the greenhouse effect.  However one of the major barriers for the large scale use of hydrogen, especially in the transportation sector, is hydrogen storage issue. There are four different technologies for storing hydrogen which are as follows: (1) Cryogenic liquid hydrogen (LH); (2) compressed gas storage; (3) metal hydride storage technology; (4) Physisorption methods. Physisorption of hydrogen in novel carbon nanostructures such as carbon nanotubes and graphene seems to be a safe and promising method for storage of hydrogen. But adsorption energy of pristine perfect carbon nanostructures is not strong enough for storing adequate amounts of hydrogen. On the other hand existence of defects can increase the hydrogen capacity, by reducing the barrier energy of dissociative hydrogen adsorption. Despite the research works have been performed so far on the adsorption of hydrogen on graphene, hydrogen interaction with different defective structures of graphene is still to be reviewed. In the present research work, ab initio calculations have been carried out to study the interaction of hydrogen with different defects in graphene. Also the barrier energies in defective graphene sheets are calculated and the results are compared with the defect-free graphene. The results indicate that defects reduce the barrier energy significantly. For instance, SW defect reduces the barrier about 41 percent relative to the perfect graphene, while 555777 and 585 defects decrease the barrier energy about 46 and 65 percent, respectively.