Pore engineering of nanoporous carbon nanofibers toward enhanced supercapacitor performance

Abstract

Porous carbon nanofibers (PCNFs) were prepared from electrospinning both without and with a pore generating inorganic material. Next, they were activated with different activation media (N-2, H2O, or CO2). The pore size was tailored from 0.64 to 0.81 nm under various activation conditions, and the specific surface area ranged from 404 to 1624 m(2).g(-1). To determine the charging mechanism of the supercapacitor in an aqueous electrolyte, the normalized capacitance was calculated, and it was compared with the adsorption behavior of the solvent, H2O, separately. The normalized capacitance showed a trend similar to that of H2O adsorption at a low relative pressure (P/P0=0.1), which was expected to be driven by the filler-pore wall interaction, indicating that the ions were strongly solvated by the solvent, H2O. The highest normalized capacitance value (32 mu F.cm(-2) at 1 mA.cm(-2)) was achieved from PCNFs having a pore size of 0.64 nm, similar to the electrolyte solvated ion sizes. It was observed that both the capacitance and H2O adsorption were achieved near the pore size of 0.64 nm and at a high functionality. It was understood that the adsorption of the solvated ions was primarily driven by the interaction of the solvent, H2O, with the surface functional groups.