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 2.1 eV, V and Cr prefer double-bond (D) sites with binding energies of 1.3 and 0.8 eV, 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 0.3–0.5 eV∕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 7.5 wt. %.