Formation of coal-based carbon nanotubes by Fe-K catalyst

Carbon nanotubes were successfully synthesized by Fe-K catalytic pyrolysis of coal. The co-pyrolysis of coal and ferrocene can only form fewer carbon nanotubes due to the few available carbon sources. Potassium carbonate can significantly eliminate the defects in the plane between the basic structural units of coal and promote the formation of carbon nanotubes, but its catalytic graphitization effect was limited when potassium carbonate was dry mixed with coal. In addition, the results show that Fe and K had a synergistic effect. Fe atoms and C atoms formed Fe-C solid solution during pyrolysis, K-based catalyst etched amorphous carbon atoms of coal, and finally Fe-K co-catalyzed the growth of a large number of carbon nanotubes with a higher degree of graphitization. The catalytic pyrolysis process had great impact on the aromatic structure and oxygen-containing functional group structure, but slight impact on the aliphatic structure of coal. The molten state of the catalyst during pyrolysis and its affinity for amorphous carbon was higher than that of graphitic carbon, leading to the migration of the catalyst and the change of crystal plane, which may be the reason for the formation of "carbon nanofiber-tube".