Periodically rippled graphene on Ru(0Â 0Â 0Â 1): A template for site-selective adsorption of hydrogen dimers via water splitting and hydrogen-spillover at room temperature

The interaction of water with periodically rippled graphene deposited on Ru(0 0 0 1) and nearly-flat graphene/Pt(1 1 1) has been investigated by using high-resolution electron energy loss spectroscopy. Graphene samples were exposed to ambient air humidity as well as to water molecules under controlled conditions in vacuum. In both cases, loss measurements show that water molecules dosed at room temperature dissociate giving rise to C-H bonds. We suggest that water molecules intercalate under graphene and are split by the underlying metal catalyst. On the lattice-mismatched graphene/Ru(0 0 0 1) interface, the corrugation of the graphene overlayer induces site selectivity for H adsorption in ortho and para dimers. On the other hand, no dimer formation occurs for the nearly-flat, multidomain graphene/Pt(1 1 1) interface.