Coal-derived nanoarchitectonics of edge-rich nitrogen-doped porous carbon nanosheets for ultralong-life zinc-ion hybrid capacitors

Rational structural tuning of carbon materials to enhance active site and achieve high edge-nitrogen doping is crucial for zinc-ion hybrid capacitors. Herein, for the first time, a strategy using g-C 3 N 4 as a self-sacrificial template and KMnO 4 as a pore-forming agent synthesizes coal-derived, edge-nitrogen-rich porous carbon sheets (KNPC). Urea thermally condenses to form a 2D g-C 3 N 4 template, providing a layered skeleton and promoting edge-nitrogen doping in the carbon precursor. KMnO 4 reacts with carbon to produce potassium salt and manganese oxide can further etching of the carbon materials to generate massive porous structure. Due to the synergistic influence, the obtained KNPC materials possess unique 2D porous nanosheet-like structure, ultrahigh specific surface area (2054.2 m 2 g −1 ), rich edge nitrogen (7.46 at. %) and oxygen (13.52 at. %) functional groups. The assembled zinc ion hybrid capacitors (ZIHCs) using KNPC as the cathode, zinc foil as the anode achieves a high energy density of 147.9 Wh kg −1 and excellent electrochemical stability (98.7 % capacity retention after 50,000 cycle tests) in 2 M ZnSO 4 aqueous electrolyte. More interestingly, the assembled flexible ZIHCs exhibit superior energy density (137.6 Wh kg −1 ) and excellent electrochemical stability (90.1 % capacity retention after 10,000 cycle tests) in ZnSO 4 /PAM gel. • Simple and efficient implementation of edge nitrogen doping. • Revealed the regulation mechanism of porous carbon nanosheets. • Assembled zinc-ion hybrid capacitors demonstrate excellent cycling stability.