Ring structure characterization of nanoporous carbon materials prepared by thermal conversion of fullerenes: Insights from ReaxFF molecular dynamics simulations

Abstract

It is challenging to prepare porous carbon materials with controllable pore sizes via the thermal conversion of fullerenes. Experimental reports have indicated that the conversion temperature and carbon source are critical factors that determine the morphology of the thermal conversion products, but the microstructure evolution and its relationship with experimental parameters are largely unknown. Here, we investigate the pyrolysis and graphitization mechanism of fullerenes during thermal conversion using reactive molecular dynamics (ReaxFF-MD) simulations. By analyzing changes in the intermediates and products formed during thermal conversion, the underlying dependence of the pyrolysis and graphitization of fullerenes on the temperature and carbon sources are revealed. We found that a higher temperature greatly accelerated the pyrolysis of fullerenes and produced an enormous variety of porous carbon products. The simulations revealed that seven-membered (7-M) carbon rings were formed between adjacent fullerene clusters during the early stage of pyrolysis. The effects observed during thermal conversion were closely related to changes in the number of 7-M carbon rings, allowing 7-M carbon rings to be used as an indicator of the pyrolysis and graphitization processes. In experiments, this knowledge can inspire researchers to obtain porous carbon materials by regulating the - formation of ring structures. This provides a new direction for the design and development of porous carbon materials with controllable morphologies and better performance.