Preparation and electrochemical studies of electrospun phosphorus doped porous carbon nanofibers

An ultra-facile fabrication process for the preparation of phosphorus doped porous carbon nanofibers (P-PCNFs) through the electrospinning and heat treatment method has been studied. The materials were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Studies showed that fabricated P-PCNFs have unique porous fibers structures, large specific surface area (462.83 cm² g^-1), and abundant microporous and mesoporous structures. X-ray photoelectron spectroscopy analyses revealed that the contents of phosphorus and electrochemical properties in a series of P-PCNF samples can be tuned by controlling the polyphosphoric acid concentration. The electrochemical properties of the materials were evaluated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Studies showed that the specific capacitance of the fabricated P-PCNFs using the ultra-facile process reached up to 228.7 F g^-1 at 0.5 A g^-1 in 1 M H₂SO₄. Over 84.37% of the initial capacitance remains as the current density increases from 0.5 to 10 A g^-1. Meanwhile, at a current density of 2 A g^-1, no capacitance loss was observed in 5000 charge/discharge cycles. The highest voltage windows of sample P-PCNFs-1.0 in 1 M H₂SO₄ aqueous electrolyte can reach 1.4 V. These properties suggest that the fabricated P-PCNFs exhibit excellent electrochemical properties. Conclusively, the surface of carbon nanofibers can be modified by heteroatom doping or surface activation which can improve the electrochemical performance of the materials.