Hydrogenation mechanism of small fullerene cages

Ab initio DFT (density functional theory) is used to investigate the hydrogenation energy and hydrogenation mechanism of Cn and CnHn fullerene cages from n = 20 to n = 60. All calculations have been performed using G03W package, with B3LYP exchange-functional and applying basis set 6–31G(d, p). It is found that the most stable hydrogenation sites on the Cn fullerene cages are ▪ and ▪ sites and on the CnHn fullerene cages are ▪, ▪ and ▪ sites. The calculations show that the required energy to initiate the hydrogen migration on the surface of Cn fullerene cages between two metastable structures of C54H is ∼1.5 eV and on the surface of CnHn fullerene cages between metastable and stable structures of the C60H61 fullerene cage is ∼2.35 eV. Also, it is found that the energy release from hydrogen migration is always enough to direct the hydrogenation process towards the most stable structures and it reduces the number of hydrogen atoms bonded to the fullerene cage via forming H2 molecules. [Display omitted] •The most stable hydrogenation sites on the Cn fullerene cages are at the ▪ and ▪ sites.•The most stable hydrogenation sites on the CnHn fullerene cages are at the ▪, ▪ and ▪ sites.•The energy release from hydrogen migration is enough to direct all cages towards the stable structures.•Forming H2 could explain the experimental finding C60Hn where n is always less than 60.