Upcycling pyrolysis fuel oil into high-performance carbon electrodes for sustainable symmetric supercapacitors

Abstract

Supercapacitor research focuses on cost-effective, sustainable energy storage, particularly using waste-derived carbon electrodes. Pyrolysis fuel oil (PFO), a by-product of naphtha steam cracking, is rich in aromatic hydrocarbons but presents refinery reprocessing challenges. This study explores PFO-based carbons as a promising electrode material, advancing waste valorization and energy storage. PFO underwent basic pitch production via bromination/dehydrobromination, followed by direct carbonization under an N2 atmosphere, while also examining CO2 activation effects. After characterizing the carbonaceous products, KOH and H2SO4 were used as electrolytes. Capacitive behavior was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD), while long-cycle performance was assessed via GCD. Moreover, electrochemical impedance spectroscopy (EIS) before and after cycling analyzed electrolyte resistance and electrochemical properties. According to the results, the highest areal capacity was achieved with the material produced using a 20 % Br ratio, CO2 activation, and H2SO4 as the electrolyte during cell assembly (83 mF & sdot;cm-2 at a 10 mV & sdot;s-1 scan rate and 133.5 mF & sdot;cm-2 at a 0.5 mA & sdot;cm-2 current density). Also, long-cycle performance was tested for 5000 cycles at 2 mA & sdot;cm-2 with no capacitance loss compared to the initial cycle. The material achieved the highest energy density (47.4 mu Wh & sdot;cm-2) and power density (1483.3 mu W & sdot;cm-2). This work paves the way for the development of scalable, low-cost carbon electrode production, which can benefit upcycling efforts by efficiently utilizing refinery by-products, thanks to PFO's excellent capacitive behavior and retention.