Valorization of Waste Heavy Fuel Oil Ash into Supercapacitor Electrodes Using Organic Electrolytes

Supercapacitors, which are characterized by rapid energy storage and release, offer a compelling alternative to traditional batteries in applications that demand high power density. However, their relatively low energy densities remain a challenge. This work explores a sustainable approach to enhance supercapacitor performance by synergistically combining nanocarbons derived from waste heavy fuel oil ash (HFOA) with a selection of organic electrolytes (BMIM-Otf, BMIM-PF6, and HMIM-TFS). We demonstrate the feasibility of converting environmentally harmful waste into valuable electrode materials while simultaneously investigating the impact of organic electrolytes on broadening the operational voltage window and boosting the energy density. Although nanocarbon was prepared, low capacitance values were observed across all electrolytes, suggesting the need for further modification of HFOA. Notably, BMIM-PF6 exhibited enhanced stability at voltages exceeding 3 V and demonstrated enhanced electrochemical performance compared to the HMIM-TFS and BMIM-Otf electrolytes, attaining an energy density of 57.45 Wh kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> at a power density of 1003.75 W kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>.