The impact of thermal stabilization temperature and duration on the pore structure of polyacrylonitrile-based carbon nanofibers

This work analyzes the impact of temperature and duration during thermal stabilization of polyacrylonitrile-based (PAN-based) nanofibers on the pore formation of carbon nanofibers. Two sample series at different stabilization durations (0–15 h) and temperatures (200–300 °C) were synthesized and characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, elemental analysis, solid state nuclear magnetic resonance and gas adsorption. A significant increase of the pore volume of the carbonized nanofibers from 0.039 cm³ g⁻¹ to 0.171 cm³ g⁻¹ was obtained for long stabilization durations (> 4 h). Similar increases up to 0.166 cm³ g⁻¹ were obtained at high stabilization temperatures (> 250 °C). This increased pore formation was assigned to the growth of larger stabilized ladder polymers and a high incorporation of oxygen during the thermal stabilization at these conditions. Both alter the structure of the final carbon nanofibers and strongly affect the formation of pore volume during carbonization. Especially, the formation of the ultramicropore volume was found to be highly dependent on these parameters. The results show the necessity of a careful consideration of the thermal stabilization conditions for tailoring of the pore structure of PAN-based carbon nanofibers.