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

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 degrees 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.