Engineering the growth and electrochemical assessments of phosphorous-doped nitrogen-based carbon nanofibers with 3D-interconnected weaving network structure for high-energy symmetric supercapacitors

The growing demand for sustainable energy sources has led to a change in attention towards developing cost-effective, high-performance energy storage devices. The construction of porous carbon network nanostructures with high surface area is complex for current-generation supercapacitors, mainly due to molecular flexibility and carbon production constraints. This work successfully produced a porous carbon nanostructure by doping phosphorous into nitrogen-based carbon nanofibers (P-doped NCNFs) utilizing a simple and controllable approach. This process entailed electrospinning diammonium hydrogen phosphate and polyacrylonitrile, subsequent high-temperature carbonization, and substantial segmented hydrogen peroxide activation processes. The P-doped NCNFs had a notable surface area of 100.69 m² g⁻¹, characterized by a distinct 3D-interconnected weaving network morphology. The 1 % P-doped NCNFs exhibited an exceptionally high capacitance of 265 ± 2 F g⁻¹ when tested in a three-electrode setup at a current density of 0.5 A g⁻¹. In addition, the constructed symmetrical supercapacitors with two identical P-doped NCNFs using a neutral Na₂SO₄ electrolyte exhibited remarkable electrochemical characteristics, which include a substantial capacitance of 225 ± 2 F g⁻¹ at a current density of 0.5 A g⁻¹, a high energy density of 30.9 Wh kg⁻¹, an excellent Coulombic efficiency of 98.8 % over 6000 cycles, an impressive power density of 250 W kg⁻¹, and significant capacitance retention of 85.6 %. These findings suggest that P-doped NCNFs could be excellent options for next-generation high-performance supercapacitors.