High-performance supercapacitors using nanostructured polyaniline-based carbon: Effect of electrolytes

Abstract

Developing high-performance materials for electrochemical energy storage devices such as batteries, and supercapacitors is a significant topic in material chemistry-based research. The high consumption and limited availability of numerous materials used in energy devices lead to the development of alternative, effective, and cost-effective materials exhibiting superior electrochemical chemical performance. A porous activated carbon, derived from polyaniline (PANI) synthesized through chemical oxidative polymerization, can be considered a viable solution in this context. In this study, the electrochemical window of the nitrogen-doped porous activated carbon was enhanced through a combined synthesis process involving the carbonization and activation of PANI nanotubes with KOH. Moreover, alternations in surface area and porosity were evaluated using BET analysis for the samples having PANI to KOH ratios 1:0.5, 1:1, and 1:2. The results revealed a significant improvement in surface area and pore volume, increasing from 18 to 3535 m²/g from pure PANI to chemically treated samples. Among those materials, the PANI to KOH ratio of 1:1 exhibited the highest surface area of 3535 m²/g and the highest pore volume of 0.7131 cm³/g. Subsequently, the electrochemical performance of all materials was evaluated using a three-electrode cell system and a symmetrical coin-cell device. Electrodes fabricated with PANI to KOH ratio of 1:1 by weight showed better electrochemical performance in an aqueous electrolyte (6 M KOH) in both systems. This material exhibited the highest capacitance of 378 F/g (at 0.5 A/g) in the three-electrode system and 143 F/g (at 0.5 A/g) in the SCCD. The SCCD achieved a maximum energy density of 23 Wh/kg with a power density of 544 W/kg. Additionally, these supercapacitors provided a good Coulombic efficiency of about 99% with capacitance retention of 97% at 7 A/g current density after 10 000 charge–discharge cycles. Further, this study expanded by investigating variations of electrochemical performance across various electrolytes, including aqueous, organic, and ionic liquids in coin-cell supercapacitors. The findings reveal promising results, suggesting potential commercial applications for this facile approach to synthesize nitrogen-doped activated carbon, especially for supercapacitors with aqueous electrolytes.