Hierarchical Porous Carbon Microfibers Derived from Tamarind Seed Coat for High-Energy Supercapacitor Application

The overwhelming interest in supercapacitors has led to the search for various carbonaceous materials, leading to hierarchical porous carbons. Herein, we report a natural biomass (tamarind seed)-based hierarchical porous carbon without any template and activated by a facile scheme. The tamarind seed coat-based hierarchical porous carbon possessed a unique configuration, making the material exhibit superior supercapacitor properties. A single carbon fiber hosting a distinctive micro- and mesoporous structure formed a connecting thread between the pores. This unique structure enabled high surface area and high capacitance. The highest surface area obtained by this method was 1702 m² g^-1, whereas the capacitance was 157 F g^-1 in 6 M KOH. Further, an ionic liquid-based electrolyte revealed 78 F g^-1 at a current density of 0.5 A g^-1. Outstanding capacity retentions of 96 and 93% were obtained over 1000 cycles at a current density of 2 A g^-1 for aqueous (6 M KOH) and ionic liquid (1-butyl 3-methyl imidazoliumbistrifluorosulfonylimide) electrolytes, respectively. The high charge-storage ability of the porous carbon microfibers (PCMFs) can be ascribed to the coexistence of micro- and mesopores. The power characteristics and the cyclic stability of PCMF materials were appealing in both electrolytes. The synthesis process described is amenable for large-scale applications with less complexity.