On the hydrogen addition to graphene

Herein, we report on a comparative study of the addition of hydrogen to graphene. The binding energies and structural parameters determined using Siesta are in excellent agreement with those calculated employing more sophisticated and computational expensive plane waves codes. The C-H binding energy between hydrogen and a graphene sheet containing Stone-Wales defects is 1.81 eV, twice as much the value computed for a perfect sheet. The single addition of hydrogen to this defect induces an important roughness on the graphene sheet. Thus, we suggest that the Stone-Wales defects are likely to be the sites where the hydrogenation of graphene originates. Finally, we have approximately estimated the free energy correction for the addition of hydrogen to graphene, with a value of 0.5 eV. The free energy change for the single H addition to perfect graphene at 298 K is spontaneous by 0.39 eV.