Nitrogen- and Oxygen-Containing Porous Ultrafine Carbon Nanofiber: A Highly Flexible Electrode Material for Supercapacitor

Herein, we report a simple and effective preparation of ultrafine CNFs (u-CNFs) with high surface area via electrospinning of two immiscible polymers [polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA)] followed by calcination at high temperature in an inert atmosphere. Various electrospinning conditions were optimized in detail. Four different kinds of PAN/PMMA ratios (10/0, 7:3, 5:5 and 3:7) were chosen and found that the PAN/PMMA ratio of 3:7 (PAN/PMMA-3:7) is the optimum one. BET analysis showed the specific surface area of the u-CNFs-3:7 was 467.57 m2/g with an excellent pore volume (1.15 cm3 g−1) and an average pore size (9.48 nm): it is about 25 times higher than the conventional CNFs (c-CNFs). TEM and FE-SEM images confirmed the ultrafine structure of the CNFs with a thinner fiber diameter of ~50 nm. The graphitic nature and atomic arrangement of the u-CNFs were investigated by Raman and XPS analyses. For the supercapacitor application, unlike the common electrode preparation methods, the u-CNFs-3:7 was used without any activation, chemical or mechanical modifications. The u-CNFs-3:7 showed a better specific capacitance of 86 F/g in 1 mol/L H2SO4 when compared to pure CNFs. The excellent physicochemical properties make the u-CNFs-3:7 an alternative choice to the existing CNFs for the supercapacitors.