High hydrogen uptake by a metal-graphene-microporous carbon network

Abstract

High-surface area carbon nanomaterials are promising candidate as reversible physisorption materials for hydrogen storage in personal transportation vehicles at moderate temperatures and pressures. Metal-incorporated graphitic microporous carbon is considered to be an excellent H2 storage material due to high molecular hydrogen uptake at the micropores coupled with considerable H2 adsorption at the graphitic network. A simple, cost-effective sputtering technique is adopted to fabricate metal-incorporated graphitic microporous carbon film and differential resistance measurements are carried out in H2 ambient to observe the high hydrogen uptake within the samples. Ultrathin amorphous carbon film is irradiated with metal nanoparticles which converts it into graphitic carbon, whereas sputtering plasma acts as dry-etchant to activate it into microporous carbon. Average number of graphene layer formation is observed to be dependent on sputtering parameters (current/voltage/time), which manifest bi-layer to multi-layer graphene sheets. With increase in the graphene layers, hydrogen adsorption also increases due to a four-fold effect - higher molecular hydrogen uptake at the graphene layers, more active sites into the micropores, promotion of molecular dissociation into atomic hydrogen by the metal nanoparticles, followed by adsorption at the active surface sites and the formation of hydrogenated carbon via destruction of the π-bonds.