The hydrogenation technique involves turning the buffer layer into a second, free-floating one-atom-thick layer of graphene by passivating dangling carbon bonds using hydrogen. This results in two free-floating layers of graphene. An additional process step fully converts the buffer layer to graphene. With this hydrogenation technique, the epitaxial graphene test structures showed a 200-300% increase in carrier mobility, from 700-900 cm2/(V s) to an average of 2050 cm2/(V s) in air and 2375 cm2/(V s) in vacuum.
More info: http://www.newswise.com/articles/adding-hydrogen-triples-transistor-performance-in-graphene