We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K2CO3 produce ACNSs having a unique combination of macro‐, meso‐ and micropores with a high specific surface area of ∼1459 m2 g−1. The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two‐electrode system. The specific capacitance (Csp) values are 55, 114, and 190 F g−1 in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF6]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg−1) and specific power (750 W kg−1) in [BMIM][PF6]. A mini‐prototype device is prepared to demonstrate the practicality of the ACNSs.
Chemically synthesized conducting polyaniline (PANI) was investigated as adsorbent for its possible application in the removal of organic dyes, such as methylene blue (MB) and procion red (PR) from their aqueous solution. PANI adsorbent behaves as a charged surface upon post-synthesis treatment of the polymer with acid and base. The adsorbent thus treated shows a high selectivity for the removal of dyes in the adsorption process. The Langmuir adsorption isotherm was used to represent the experimental adsorption data. The cationic dye, MB can be preferentially removed by the base-treated PANI while the anionic dye, PR is predominately removed by the acid-treated one. These observations were further evidenced from the measurements of molar conductance and pH of the dye solutions employed for adsorption. The finding can be explained considering the electrostatic nature of adsorption coupled with the morphology of the PANI surface thus treated.
Supercapacitor is considered a promising energy storage device due to its high‐power density and high specific capacitance. Electrode materials and electrolytes are major components of supercapacitors. The most used electrolytes are not biocompatible, which limits their practical applications. Bio‐electrolytes often cause low performances of supercapacitors. However, the inadequate performances of bio‐electrolytes for supercapacitor applications could be improved using redox molecules. Here, we are reporting the development of a novel redox bio‐electrolyte based on pivalic acid (PA) and ascorbic acid (AA). The salts of PA and AA served as the bio‐electrolyte and redox molecules, respectively. It is worth to note that PA which can be generated from bio‐sources and industrial wastes, is soluble in alkaline solutions. AA is found in most living organisms, including plants. The developed supercapacitor with the bio‐based redox electrolyte provides a specific capacitance of 308 Fg−1 at a current density of 1 Ag−1 and achieved an energy density of 15 Whkg−1 at a power density of 300 Wkg−1. The supercapacitor demonstrates a good coulombic efficiency of ∼97% with capacitance retention of ∼72% after 10000 charge‐discharge cycles. This study is expected to widen the applications of bio‐based redox electrolytes for practical electrochemical energy storage applications and enables access to greener and more sustainable energy storage technology.
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