Augmenting the supercapacitive performance of candle soot-derived activated carbon electrodes in aqueous and non-aqueous electrolytes

Supercapacitors are attracting the scientific community because of their advantages, such as ultra-long-life cycles and high-power density. Nevertheless, they pose one of the critical challenges of low energy density. In the present work, this challenge is addressed by two different approaches. One strategy uses carbon from candle soot activation, which resulted in a high surface area of 1060 m² g⁻¹ and retained capacitance of 82 % for 10,000 cycles in the aqueous (H₂SO₄) electrolyte. In another approach, energy density is increased by employing non-aqueous electrolytes (tetraethylammonium tetrafluoroborate in acetonitrile (TEABF₄-ACN) and 1-ethyl-3-methylimidazolium (EMIMBF₄)), which showed a wide electrochemical stability window and specific energy of 15 and 37.5 Wh kg⁻¹, respectively. However, this non-aqueous liquid provides challenges like high cost, poor ionic mobility, and high viscosity. A redox additive (0.02 M hydroquinone (HQ)) electrolyte is utilized to tackle these challenges. This electrolyte enhanced the electrochemical potential window to 0–2.2 V and delivered a specific energy of 61.6 Wh kg⁻¹.