Collective stabilization of hydrogen chemisorption on graphenic surfaces

A graphene sheet is well known to be highly stable against chemisorption of a single hydrogen atom, since a puckered ${\mathrm{sp}}^3$ hybridized site heavily distorts the surrounding ${\mathrm{sp}}^2$ framework. However, successive adjacent chemisorbed hydrogen atoms can engage in a collective stabilization mediated by cooperative alternate puckering in the underlying carbon sheet. After several chemisorbed atoms, the binding energy for further adsorption changes sign and becomes favorable. This process requires access to both sides of the graphene sheet. Therefore it is suppressed on a graphite surface, but may be accessible in carbon nanotubes, if the initial kinetic barrier to creating the nucleation island can be overcome.