Sustainable Carbon Electrode From Rice Straw—Engine Oil Co‐Activation: Electrochemical Performance

ABSTRACT In this study, a nano‐structured carbon material with partially graphitic features was synthesized as a sustainable alternative to fossil‐derived carbon. A series of characterization techniques revealed an enrichment of oxygenated C─O/O─C═O functionalities alongside a reduction of O─H, C═O, C─H, and C═C groups, highlighting the potential of the activation strategy. Further, the electrochemical performance of the carbon electrode fabricated from engine oil (EO) co‐activated carbon (AC) was investigated. Comparative capacitances using cyclic voltammograms studies with 0.5 M KCl aqueous electrolyte achieves 9.31–11.34 F/g at 100 mV/s, with enhanced charge storage by 21.8% across metrics. Co‐AC electrode exhibits a pronounced high‐frequency semicircle (Rct ≈ 0.7 kΩ) transitioning to depressed capacitance, confirming oxygen‐mediated charge transfer processes.