Based on the density functional theory, we investigate and discuss how hydrogen behaves at the edges of graphite sheets/layers, in particular the zigzag edge. Our calculation results show that the zigzag edge is very reactive. It is possible to dissociatively adsorb H2 on these surfaces without any activation barrier hindering the reaction. To be able to use carbon nanomaterials as a means to store hydrogen, one of the crucial factors necessary would be the ability to dissociate hydrogen first, and then (somehow) induce them to stick to the carbons on each sheets. The results we present here suggest the possible utility of the zigzag edge as a reaction channel to carry out the aforementioned process.

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We performed quantum dynamics calculations using previously obtained potential energy surfaces (PESs) for the dissociative adsorption of hydrogen molecule incident on a Mg(0001), Ti(0001), and La(0001) surface. Based on the sticking probability plots we obtained as functions of the incidence H 2 beam energy, La is the best material for hydrogen storage, followed by Ti, and then by Mg. This is due to the absence of an activation barrier in the H 2 /La(0001) system. Both H 2 /Ti(0001) and H 2 /Mg(0001) systems have activation barriers, but the H 2 /Ti(0001) system has a very small activation barrier far from the curved region of the reaction path, while the H 2 /Mg(0001) system has a high activation barrier close to the curved region along the reaction path. Our results also indicate that the sticking probability has some dependence on the vibrational state of the impending H 2 molecule for the Mg, Ti and La surfaces. The degree of dependence still varies in each metal. Vibrational effect is most observed with Mg, followed by Ti, and then by La.