Fabrication, structure and supercapacitance of flexible porous carbon nanobelt webs with enhanced inter-fiber connection

Flexible carbon nanobelt webs (CNBWs) with a hierarchical porous structure, considerable N- and/or O-containing surface functionalities were fabricated by electrospinning of phenolic resin/PVP/magnesium nitrate (MNH) solution, followed by curing, thermal treatment and picking. The effect of spinning humidity on the morphology of cured fibers was investigated. The results showed that low humidity was required for successful spinning and collection of the nanobelts. The addition of MNH played a crucial role in inhibiting inter-nanobelt adhesions and warping of nanobelts during thermal treatment and producing hierarchical porous structure. The increase in MNH content resulted in an enhancement in the specific surface area (SSA), micropore volume, and mesoporosity of the CNBWs. The achieved CNBWs displayed the maximum SSA of 779 m2 g−1 and a mesoporosity of 82%. The reduction in the number of warping endowed the CNBWs with face-to-face inter-nanobelt connection, then brought about a significant enhancement in conductivity and packing density of the CNBWs, which ultimately improved the rate performance and volumetric capacitance. The work proposed a feasible route for improving the conductivity and volumetric capacity of electrospun carbon nanofiber webs as the electrode for supercapacitors or batteries.