H_2 Dissociative Adsorption at the Armchair Edges of Graphite

TL;DR

This study uses density functional theory to analyze hydrogen dissociation at graphite edges, revealing an activation barrier at armchair edges and difficulty in desorption, contrasting with zigzag edges.

Contribution

It provides new insights into hydrogen behavior at armchair edges of graphite, highlighting barriers and adsorption characteristics not previously detailed.

Findings

Activation barrier hinders H_2 dissociation at armchair edges

Hard to desorb hydrogen once adsorbed at armchair edges

Unlikely to find H_2 molecules between plain graphite sheets

Abstract

We investigate and discuss how hydrogen behaves at the edges of a graphite sheet, in particular the armchair edge. Our density functional theory-based calculations results show that, in contrast to the zigzag edge [cf., e-J. Surf. Sci. Nanotech. 2 (2004) 77], regardless of orientation, there is an activation barrier hindering H_2 dissociation at the armchair edges. And once they do get dissociatively adsorbed at the armchair edges, we find that it would be extremely hard to desorb the H from their adsorption sites at the armchair edges. Furthermore, we also found that, consistent with our earlier conclusions [cf., J. Phys. Soc. Jpn. 72 (2003) 1867], it is unlikely that we would find a whole H_2 in between plain graphite sheets.