Flexible nanoporous nitrogen-doped graphene film (PNGF) prepared by facile hydrothermal ammonia reaction of nanoporous graphene oxide film (PGOF) is reported. The specific capacitance of the PNGF are 468 F g−1 at a scan rate of 2 mV s−1. The capacity retention after 10,000 charge/discharge cycles at a current density of 1 A g−1 is more than 81%. Two-electrode symmetric supercapacitor in a 6 M KOH aqueous electrolyte solution was fabricated, delivering a maximum power density of 5000 W kg−1 (at the energy density of 4.17 W h kg−1) and the maximum energy density of 6.43 W h kg−1 (at the power density of 150 W kg−1). The enhanced electrochemical performance can be attributed to nitrogen doped and the unique graphene film nanostructure. The expansion nanoporous structure of layer by layer plays the role of an “ion-buffering” reservoir, offering nano-channels for liquid electrolyte penetration by enlarging the specific surface area of PNGF efficiently. This flexible nanoporous gaphene film significantly suggests a broad range of application for fabricating high performance and novel energy storage devices.
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