Polyacrylonitrile-Based Composite Carbon Nanofibers with Tailored Microporosity

Carbon nanofibers are currently used in many applications including electrochemical power sources, particularly, fuel cells. Their properties are highly dependent on the micro- and mesoporous structure. Here we provide a porosimetric analysis of the polyacrylonitrile-based electrospun composite Zr- and Ni-containing carbon nanofiber mats by N2 and CO2 adsorption methods for the first time. It was found that pyrolysis temperature affects specific surface area and volume: the values increase for the sample pyrolyzed at 900 °C compared with the initial stabilized nanofibers (300 °C, air) according to the Dubinin --- Radushkevich, non-local density functional theory (NLDFT) and grand canonical Monte-Carlo methods (GCMC). For higher pyrolysis temperatures (1000 and 1200 °C), the porosimetric parameters decrease compared with the one pyrolyzed at 900 °C. According to the NLDFT and GCMC pore size distribution, the difference for pyrolyzed samples is mostly related to a sharp decrease in the specific surface area for pores with a size of ~ 0.5 nm and an increase for pores at 0.55--0.8 nm compared with the initial stabilized sample. The study demonstrates a way to adjust porosimetric parameters depending on the pyrolysis conditions of the nanofiber mats, since it can improve characteristics of such type of carbon materials in electrochemical devices