Light Alkaline-Earth-Metal Coated Carbon Fullerenes as Effective Hydrogen Storage Media

We propose functionalizing carbon nanostructures with light alkaline-earth metals for use as hydrogen storage media. To support this idea, we investigate the feasibility of coating C$_{60}$ fullerenes with light alkaline-earth metals and analyze the hydrogen storage capacities of the resulting compounds. We find a new and unique binding mechanism responsible for the strong binding between Ca or Sr atoms and C$_{60}$. Our theory explains experiments showing that C$_{60}$ can be evenly covered by a monolayer of Ca or Sr atoms. The coating results in a charge redistribution leading to electric dipolar fields around the metal atoms through which the fullerene surface becomes an ideal hydrogen-attractor with a binding strength larger than that of alkali carbon complexes but small enough to prevent hydrogen dissociation as in the case of transition metal decorated fullerenes. With a hydrogen uptake of more than 8.4wt\% and a binding energy of $\approx$ 0.4eV/H2 on C$_{60} $C$_{32}$ Ca is superior to currently used coating elements.