Dynamics of Hydrogen Spillover on Carbon-Based Materials

We investigate the dynamics of physisorbed atomic hydrogen on several carbon based materials (various fullerenes and a graphene sheet) using first principles molecular dynamics simulations. The physisorbed H atoms, generated upon H-2 dissociative chemisorption on metal catalysts and interaction with carbonized "bridge" materials and substrates (Chen, L.; et al. J. Phys. Chem. C 2007, 111, 18995), can diffuse freely on carbon surfaces with high mobility. Our results indicate that physisorption of H atoms is a metastable state and the atoms will readily recombine to form H-2 molecules, which can be recycled to generate more H atoms, or attack the substrates to form C-H bonds. The strength of the resulting C-H bonds exhibits a strong dependency on the carbon material surface curvature. The implication of C-H bond strength on the dehydrogenation of hydrogenated carbon materials to form molecular H-2 is discussed.