Graphene showed an unusually high hydrogen storage capacity as well as a unique, slow hydrogen adsorption process compared with a variety of carbon materials (carbon nanotubes, activated carbons, mesoporous carbons, templated carbons, and metal organic frameworks). Catalytic dissociation of hydrogen on graphene is observed for the first time. The hydrogen dissociation rate on graphene is also significantly faster than the adsorption rate. This leads to the conclusion that the most active sites on graphene for hydrogen dissociation are not the only sites where the enhanced adsorption occurs. The mechanistic differences in adsorption on graphene when compared with the other carbons are further demonstrated by differences in temperature-programed desorption results and heats of adsorption. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 2902-2908, 2011