Hydrogen storage using functionalized saturated hydrocarbons

Saturated hydrocarbons, though relatively inert in nature, may become more reactive by functionalization. Using first-principles computational methods, we perform a systematic search for functional groups to be attached to saturated hydrocarbons for high-capacity storage of molecular hydrogen. When a saturated hydrocarbon such as propane is functionalized with OH, NH2, or SH, a transition metal atom may be strongly bound to each functional group. We find that hydrogen molecules are adsorbed on transition metal atoms with the binding energy suitable for reversible processes (adsorption and desorption) under practical hydrogen storage conditions. We also show that the functional groups may help reduce the tendency for transition metal clustering. The maximum gravimetric storage densities range from 8.7 wt% to 12.6 wt% depending on different materials. We explain the mechanism of multi-dihydrogen adsorption on a transition metal atom by generalizing the Kubas model.