Edge-decorated graphenenanoribbons by scandium as hydrogen storage media

Abstract

On the basis of density functional theory calculations, we show that edge-decorated graphene nanoribbons (GNRs) by scandium can bind multiple hydrogen molecules in a quasi-molecular fashion. The average adsorption energy of H₂ on Sc ranges from 0.17 to 0.23 eV, ideally suited to hydrogen storage. For the narrowest GNR with either armchair or zigzag edges, the predicted weight percentage of H₂ is >9 wt%, exceeding the gravimetric target value set by the Department of Energy (DOE). The bonding energy between Sc and the GNR is significantly greater than the cohesive energy of bulk Sc so that clustering of Sc will not occur once Sc is bonded with carbon atoms at the edge of GNRs. Moreover, the adsorption energy of H₂ can be modestly tuned (either enhanced or reduced) by applying an external electric field.