Hydrogen storage by spillover on graphene as a phase nucleation process

Hydrogen chemisorption on graphene receptor-substrate is of great interest for energy storage. However, it is difficult to reconcile with a single H atom binding to carbon being weaker than it is within initial molecular H-2. This paradox is resolved by presenting the process as phase nucleation in the reaction Rec(solid)+H-2(gas)<->(H center dot Rec)(solid), with the nucleus' energy separable into the Gibbs formation potential and the interface part. Atomistic calculations bridge remarkably with the macroscopic-continuum description and show a feasible path to 7.7 wt % H content at nearly ambient conditions.