Molecular and dissociative adsorption of multiple hydrogen molecules on transition metal decorated C60

Recently we have predicted [Phys. Rev. Lett. 94, 175501 (2005)] that Ti-decorated carbon nanotubes can adsorb up to 8 wt.% hydrogen at ambient conditions. Here we show that a similar phenomenon occurs in light transition-metal decorated C60. While Sc and Ti prefer the hexagon (H) sites with a binding energy of 2.1eV, V and Cr prefer double-bond (D) sites with binding energies of 1.3 and 0.8eV, respectively. Heavier metals such as Mn, Fe, and Co do not bond on C60. Once the metals are adsorbed on C60, each can bind up to four hydrogen molecules with an average binding energy of 0.3-0.5eV H2. At high metal coverage, we show that a C60 can accommodate six D-site and eight H-site metals, which can adsorb up to 56 H2 molecules, corresponding to 7.5wt.%.