Hierarchically porous activated carbon electrodes synthesized from expired tablets for high-performance supercapacitor and photocatalysis application

Hierarchically porous activated carbons (HACs) were derived from expired tablets through facile carbonization with the aid of H₃PO₄ activation. The enhanced specific surface area (SSA) and porous architecture of the derived ACs were confirmed using standard characterization techniques. The as-prepared HACs exhibited an improved specific capacitance (CS) of 141.8 F/g at 2 A/g, with a cyclability of 70% after 2,000 repeated charge–discharge cycles. The HACs//HACs symmetric supercapacitor (SC) device demonstrated a CS of 46.8 F/g at 2 A/g. Additionally, the HACs//HACs symmetric device exhibited the highest energy density of 12.7 Wh/kg and a power density of 4656.5 W/kg. The HACs//HACs device also displayed exceptional cyclability, maintaining 80.2% retention after 3,000 charge/discharge cycles at 20 A/g. Furthermore, the photocatalytic activity of both ACs and HACs was assessed under visible light through the photodegradation of Reactive Black 5 (RB5) dye in aqueous solution. The results indicated that the HACs exhibited excellent photocatalytic activity, with approximately 80% degradation after 120 min, compared to the ACs. These findings demonstrate that the HACs electrode is a cost-effective, eco-friendly, and promising candidate for high-performance energy storage applications.