Microporous Organic Polymer‐Derived Nitrogen‐Doped Porous Carbon Spheres for Efficient Capacitive Energy Storage

Abstract A facile and template‐free synthetic approach was utilized to obtain a series of nitrogen and oxygen‐doped microporous carbon spheres (CTS‐X‐700) from carbazole‐terephthalaldehyde based co‐polymer spheres (CTS). The inherent spherical morphology of the co‐polymer remained intact even after activation at high temperature (700 °C). The synthesized materials exhibit BET surface area of up to 1340 m 2 g −1 with an interconnected porous network consisting of ultramicropores and supermicropores along with a small amount of mesopores. Moreover, a good balance of heteroatom surface functionalities (N content up to 3.2 % and O content up to 12 %) was maintained without compromising the porosity by systematically varying the activation conditions. These features result in a high specific capacitance value of 407 F g −1 at 1.0 A g −1 in aqueous acid electrolyte with a three‐electrode system and superior cycle stability of 100 % capacitance retention even after 10000 cycles. Furthermore, the high energy density (10.6 W h kg −1 at a current density of 0.5 A g −1 ) in an aqueous electrolyte of the assembled supercapacitor device further demonstrates the possible applications of the synthesized materials as high‐performance energy storage devices.