Freestanding electrodes based on nitrogen-doped carbon nanofibers and zeolitic imidazolate framework-derived ZnO for flexible supercapacitors

This study investigates the carbonization of electrospun fibers derived from zeolitic imidazolate framework (ZIF)-7/polyacrylonitrile solutions containing urea or polyvinylpyrrolidone (PVP). The carbonization yields highly flexible composites comprising nitrogen-doped carbon nanofibers and ZnO. Notably, using PVP as a nitrogen source generates a composite exhibiting excellent electrochemical performance. Specifically, it delivers a high capacitance of 382.5 mF cm⁻² at a current density of 1 mA cm⁻². Furthermore, this composite demonstrates capacitance retentions of approximately 101 % and 80 % after 10,000 cycles and a 90° bending test, respectively. The charge-storage capability of the PVP-based ZnO_P/C composite surpasses that obtained without PVP by 1.4 times. Additionally, a composite fiber mat of ZnO_P/C obtained via one-step electrospinning exhibits exceptional electrical conductivity and an energy density of 49 μWh cm⁻² at a power density of 2 mW cm⁻². These findings highlight the potential of this material as an electrode for supercapacitors.