Pyrolysis of Epoxidized Fullerenes Analyzed by Spectroscopies

Epoxide is one of the simplest functional groups on fullerenes, but mechanisms for migration of oxygen atoms and formations of CO and CO2 gases upon heat treatment are still unclear. In this work, epoxidized fullerenes were heated in helium gas up to 673 K and the pyrolyzed structures of epoxidized fullerenes were analyzed using X-ray photoelectron spectroscopy, infrared spectroscopy, direct-injection mass spectrometry, elemental analysis, and density functional theory calculation. Functional groups such as C=0 and lactone groups were formed by heat treatment of the epoxidized fifflerenes at 523 K. At 673 K, lactone groups were decomposed into CO and CO2 gases. The amount of the CO2 gas was more than that of the CO gas. This suggests that a formation of CO2 gas from lactone groups is energetically more favorable than that of CO gas. Moreover, the ratio of CO2 gas to CO gas increased, as the amount of oxygen atoms on fullerenes increased. The formation of CO and CO2 gases at 673 K indicates that the presence of carbene sites with either vacancy defects or ether groups on fullerenes.