Fabrication of Phyllanthus emblica leaves derived high-performance activated carbon-based symmetric supercapacitor with excellent cyclic stability

Porous carbon as an electrode material for supercapacitors has received attention due to its large surface area, excellent electrochemical stability, environmental sustainability, and low-cost scalable production. In this work, we have synthesized activated carbon from waste biomass of Phyllanthus emblica leaves (PELAC) and used it as an electrode material for supercapacitor application. PELAC discloses hierarchical porosity with a high surface area of 1244 m2 g-1 and displays the maximum specific capacitance of 336 F g-1 @ 1 A g-1 using 6 M KOH electrolyte as compared to 1 M Na2SO4 (250 F g-1) and 6 M NaOH (290 F g-1). In KOH electrolyte, good cycling retention (during the course of 24,000 GCD cycles) is achieved as; 98.7 % up to initial 8000 cycles @ 10 A g-1, 96 % up to middle 8000 cycles @ 20 A g-1, and 89 % up to final 8000 cycles @ 30 A g-1 for the same PELAC electrode. Further, to evaluate the supercapacitor performance for a practical device, the symmetric supercapacitor (SSC) device was constructed using PELAC as electrodes with PVA/KOH gel as an electrolyte. The device offers a maximum energy density of 29 W h kg-1 and a higher specific power of 6750 W kg-1. Remarkably, the device unveils an outstanding cycling stability of 95 %, which retained up to 25,000 recurring GCD cycles at high current density of 16 A g-1. Moreover, when two SSC devices were connected in series, the assembly enlightened red and yellow LEDs with good brightness. The long-term durability with a practical demonstration of the present device marks PELAC can be a sustainable and cost-effective candidate for electrochemical energy storage applications.