Electrochemical Performance of Indian Loofah-Derived Carbon in Aqueous Electrolytes for Supercapacitor Electrode

Abstract

Tailoring the electrode-electrolyte combination is an important strategy for improving the charge storage kinetics of supercapacitive devices. Here, the effect of aqueous electrolytes (3 KOH, H2SO4, Na2SO4) on the electrochemical response of Indian loofah-derived activated carbon (AC) prepared via controlled carbonization and NaOH-assisted hydrothermal activation is examined. The electrodes exhibit high specific capacitance (at 1 mV s-1) of 362.28 F g-1 in H2SO4 and 336 F g-1 in KOH, decreasing significantly to 147.81 F g-1 in Na2SO4. Additionally, it demonstrates an excellent capacity retention of 98% (10 000 cycles), a wide voltage (approximate to 1.1 V) window and delivers an energy density of 38.08 Wh kg-1 at 549.99 W kg-1 in 3 KOH compared to others. It is attributed to the ionic mobility, hydration radius, conductivity, and interactions of the electrolytic ions with surface functional groups of AC. Besides, symmetric AC cells using a 3 KOH aqueous solution outperform their solid-state counterparts (3 KOH + Polyvinyl Alcohol), delivering 215 F g-1 (at 1 mV s-1) and 20.93 Wh kg-1 (at 500 W kg-1). These findings provide key insights into optimizing electrode-electrolyte synergy for high-performance energy storage systems.