Optimization of the pore structure of PAN-based carbon fibers for enhanced supercapacitor performances via electrospinning

Activated microporous polyacrylonitrile-based carbon nanofibers (APCFs) were synthesized by a sequential process of electrospinning, carbonization, and KOH activation. The porosity and surface chemistry of the APCFs strongly depended on the activation temperature. The specific surface area and pore volume varied from 15 to 1886 m² g⁻¹ and 0.021–1.196 cm³ g⁻¹, respectively, as the activation temperature increased; this was accompanied by morphology changes at high temperature. The dominant microstructure and minor mesostructure improved the capacitance of carbon. Compared to the other samples, APCFs activated at an optimum temperature of 1000 °C showed the highest specific capacitance of 103.01 F g⁻¹ at 1 A g⁻¹ in 1 mol L⁻¹ Na₂SO₄ aqueous electrolyte, and an excellent cycling durability up to 3000 cycles. The improved electrochemical efficiency could be explained by the high specific surface area, suitable pore size, and influence of heteroatoms relative to the increased electrical double-layers. The change in the pore size distribution with activation temperature is also discussed in detail.