Electrospun activated carbon nanofibers for supercapacitor electrodes

Porous activated carbon nanofibers have been prepared by electrospinning a H₃PO₄-containing polyacrylonitrile precursor. A small amount of H₃PO₄ (<1 wt%) serves as the activation agent during carbonization of the nanofibers. The activated carbon nanofibers have a large surface area (∼709 m² g⁻¹) and high porosity (0.356 cm³ g⁻¹). A high specific capacitance of 156 F g⁻¹ (at 0.5 A g⁻¹) is obtained at a 1 : 10 mass ratio of H₃PO₄ to polyacrylonitrile. The energy density of the supercapacitor with the activated carbon nanofibers as the electrodes reaches 10.98 Wh kg⁻¹ at a power density of 10 kW kg⁻¹. This is ∼9 fold larger than that of carbon nanofibers without H₃PO₄ because the H₃PO₄-based activation process significantly increases both the micropore volume and the volume ratio of mesopores to micropores.