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Abstract:
Functional porous carbon nanospheres with tunable textural properties and nitrogen functionalities were synthesized from cheap and sustainable phenolic carbon precursor (tannic acid) and nitrogen precursor (urea) using a facile one-step salt-templating method. The diverse functional carbons were obtained by calcination of mixtures of different molar ratios of urea to tannic acid (0:1, 5:1, 9:1, 13:1 and 17:1) with a eutectic salt (NaCl/ZnCl2) that was used as porogen. Physico-chemical characterization of obtained microporous carbons demonstrated that textural properties, morphology, surface functionalities, and conductivity were strongly influenced by molar ratio of urea to tannic acid. The nitrogen content in the carbons increased with the molar ratio of urea, reaching a maximum of 8.83 % N at the highest molar ratio while the specific surface area (SBET) of microporous carbons varied from 890 m2g-1 to 1570 m2g-1 depending on the synthesis conditions. Electrochemical performance of carbon nanospheres in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI) was also significantly influenced by the synthesis conditions due to combined effect of textural properties, morphology, nitrogen functionalities and electrical conductivity. Supercapacitors based on functional porous carbon synthesized with a molar ratio of urea to tannic acid of 9:1 exhibited the best performance, with specific capacitance as high as 110 Fg-1 and real energy density of 33 Whkg-1, when charged-discharged at 3.5V in PYR14FSI.
