Carbothermal process-derived porous N-doped carbon for flexible energy storage: Influence of carbon surface area and conductivity

[Display omitted] •N-doped carbon (NC) with tunable properties is obtained using carbothermal method.•Simultaneous production Zn nanotubes results in waste-free approach.•Charge storage capacity of NC precisely studied against conductivity/surface area.•High capacitance of 229 F/g with exceptional rate capability is observed for NC.•Ultra-high stability is retained with flexible prototype solid state device. A simple and scalable method to synthesize N-doped carbon (NC) based on a carbothermal reduction of a ZnO/carbon composite (ZCC) obtained from the decomposition of a zinc aniline nitrate complex is reported. The present study examined the effects of the structural characteristics of NC, such as electrical conductivity and surface area, more precisely without altering the other structural features of NC. A carbothermal reduction of ZCC allowed the production of hierarchically porous NC with a low sheet resistance of 0.432 kΩ □−1 without any post-treatment with Zn nanorods as a valuable byproduct. The resulting NC exhibited ultra-high stability and rate capability, i.e., 100% stability after 200,000 cycles up to 300 A g−1 with a high capacitance of 229 F g−1 at 0.5 A g−1. The 288% increase in surface area with a similar % contribution from micro and mesopores and similar electrical conductivity increased the electrochemical charge storage capacity of NC by 266%. Similarly, NC materials possessing a similar surface area but a large difference in electrical conductivity resulted in a 1539% difference in charge storage capacity. Enhancement of both the surface area and electrical conductivity improved the capacitance of NC drastically to 4098% higher than the base product. A prototype flexible solid-state supercapacitor fabricated from the obtained NC delivered a very high areal capacitance of 363.6 mF cm−2 (at 0.5 mA cm−2) with ultra-high stability (82%) even after 70,000 cycles (at 25 mA cm−2).