Performance optimization of the symmetric supercapacitors based on paddy straw-derived porous activated carbon

The utilization of porous carbon material derived from sustainable, cost-effective, and renewable biomass for supercapacitor electrode applications has garnered significant attention in recent times. In this work, activated carbon was synthesized via the carbonization of paddy straw, succeeded by activation using different molarity levels (3 M to 6 M) of the activating agent. X-ray diffraction, fourier-transform infrared spectroscopy, N2 physisorption, and field-emission scanning electron microscopy were employed to characterize various parameters of the synthesized activated carbon derived from paddy straw (ACP). The process of activation considerably increased the specific surface area up to 1358.087 m2 g−1 establishing a well-developed intercalated tunnelled porous surface morphology that promotes charge accumulation. The electrochemical characteristics of the activated carbon were evaluated in a 6 M KOH electrolyte using techniques such as cyclic voltammetry, galvanostatic charge-discharge tests, and impedance spectroscopy. The highest specific capacitance of 396 F g−1 at the current density of 1 A g−1 was obtained for the single electrode of ACP-5 M. At a current density of 1 A g−1 the symmetric ACP-5 M based symmetric device provided a specific energy of 38.8 Wh k g−1 at a specific power of 604 W k−1. The paddy straw-derived activated carbon demonstrates versatile potential as an electrode material for energy storage applications due to its impressive electrochemical properties, well-developed porosity, and remarkable capacitance retentions of 90.6 % in 6 M KOH following 10,000 charge-discharge cycles.