Water Hyacinth-Derived Hierarchical Porous Activated Carbon as a Supreme Electrode Material Toward the Stellar Performance in Supercapacitor Applications

Abstract

Activated carbon (AC) is gaining more attention as a cost-effective, efficient electrode material for supercapacitors due to its larger surface area and porous structure. Optimizing factors like activation holding time is the key to achieving AC with high surface area and hierarchical pores. Herein, AC from water hyacinth, a common biowaste, was prepared using the KOH activation process, with varied holding times (∼0.5, 1.5, and 2.5 h) to study their impact on surface area and specific capacitance. HAC2 (activation holding time 1.5 h) exhibited an elevated surface area of ∼540 m² g^–1. The optimal HAC2 electrode afforded a high specific capacitance of ∼323 F g^–1 at 1 A g^–1. Considering a practicability perspective, HAC2 was used as an electrode material in aqueous and organic symmetric supercapacitor devices, achieving specific capacitances of ∼173 and 34 F g^–1 at 0.5 A g^–1. To achieve a high specific capacitance and a high potential window, the MoO₃//HAC2 device was assembled. This device achieved a high specific capacitance of ∼104 F g^–1 at 0.5 A g^–1 with an outstanding energy density of 28.58 W h kg^–1 at 351 W kg^–1 power density and a capacity retention of ∼86% after 10,000 cycles. The developed device can power a digital clock and an LED, indicating that it can be potentially used as an energy storage device.