Comparative study of hydrofullerides C60Hx synthesized by direct and catalytic hydrogenation

Hydrofullerides with hydrogen content up to 5 wt. % were obtained by direct and catalytic reactions with H-2 gas. Hydrogen content was monitored 'in situ' using a gravimetric system, and verified by chemical analysis 'ex situ'. It was found that pure C-60 reacts rapidly when exposed to H-2 gas at 673 K and 50-100 bar. Gravimetric study of this reaction showed that hydrogenation is saturated at about 5 wt. % of hydrogen. The mass of the sample goes through a maximum and with a longer reaction time its weight starts to decrease. This proves that hydrofullerides with high hydrogen content are not stable and strong hydrogenation results in the collapse of C-60 molecules. XRD studies showed that samples prepared by direct hydrogenation without a catalyst retain an original fcc structure with an increase of the cell parameter a up to 15.1 Angstrom. Catalytic hydrogenation of C-60 with H-2 gas results in a decrease of the reaction temperature and formation of hydrofullerides with different types of crystal structures.