Abstract
We explore theoretically the feasibility of functionalizing carbon nanostructures for
hydrogen storage, focusing on the coating of C60 fullerenes with light alkaline-earth metals. Our
first-principles density functional theory studies show that both Ca and Sr can bind strongly to
the C60 surface, and highly prefer monolayer coating, thereby explaining existing experimental
observations. The strong binding is attributed to an intriguing charge transfer mechanism
involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise
to electric fields surrounding the coated fullerenes, which can now function as ideal attractors
upon molecular hydrogen adsorption with binding strengths strong enough for potential room
temperature applications but weak enough to avoid H2 dissociation. With a hydrogen uptake of
>8.4wt% on Ca32C60, Ca is superior to all the recently suggested metal coating elements.
