Nitrogen-enriched hierarchically porous carbon nanofiber network as a binder-free electrode for high-performance supercapacitors

•NHCFs were synthesized using ZIF-8/PAN as precursors.•NHCFs have hierarchical pores structure and ultrahigh nitrogen content.•NHCFs demonstrated a high specific capacitance (302 F g−1 at 0.5 A g−1).

Nitrogen-enriched hierarchical porous carbon nanofibers (NHCFs) are promising candidates for supercapacitors. However, the synthesis of these carbons with high N content and large specific surface area is still great challenging. Here, a flexible NHCF paper is fabricated by electrospinning zeolitic imidazolate framework-8 (ZIF-8) suspended in polyacrylonitrile (PAN) solution, followed by a combined heating and acid treatment. The specific surface area and N content of the prepared NHCFs can be controlled by varying the amounts of ZIF-8 and calcination temperature. The highest specific surface area (559 m2 g−1), ultrahigh N content (15.59 wt%) and best electrochemical performance can be obtained from the calcination of PAN/ZIF-8 (66.7 wt%) at 800 °C, with a maximum specific capacitance of 302 F g−1 at a current density of 0.5 A g−1. In addition, the specific capacitance up to 146.7 F g−1 can still be obtained at high current density of 40 A g−1. The excellent electrochemical performance can be attributed to the synergetic effect of high nitrogen content, hierarchical porous structure and high specific surface area.