No abstract

Nitrogen-doped porous carbons have been synthesized from triazine based polyimide frameworks using ZnCl2 as an activating agent for electrochemical 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 °C). The synthesized materials exhibit BET surface area of up to 1340 m2 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.

Nitrogen-doped porous carbons are synthesized by KOH activation of hypercrosslinked 1,1,2,2-tetrakis (4-(9H-carbazol-9yl)phenyl)ethene (HTCP) polymer for efficient supercapacitor application. The obtained materials possess combined microporous and mesoporous structures with high BET surface area of upto 2226 m 2 g À 1 and nitrogen content of upto 2.62%. These structural properties result in increased accessible surface and redox sites for enhanced electrochemical capacitive storage. Effects of nitrogen functionalities and carbonization temperature on the porous materials are studied by monitoring the capacitive behaviours of the samples. The material afforded by carbonization of HTCP at 700°C (HTCP-700) offers a high specific capacitance of 445 F g À 1 (1 A g À 1 ) and excellent cycle durability of nearly 100% retention upto 10000 cycles in 1 M H 2 SO 4 electrolyte. The cyclic voltammetry and galvanostatic charge-discharge experiments indicate a good rate capability (278 F g À 1 at 20 A g À 1 ). The supercapacitor device fabricated with PVA-H 2 SO 4 gel electrolyte using HTCP-700 as an active material delivered maximum energy density of 11.6 W h kg À 1 .[a] N.