From nutshells to energy cells: Pioneering supercapacitor electrodes via innovative argan nutshell activated carbon synthesis

In this work, a detailed comprehensive investigation explores the impact of processing methods and chemical activation parameters on the textural properties of a series of activated carbons (ACs) derived from Argan Nut Shell (ANS) residue using KOH. This study aims to develop and optimize high-quality ACs for use as solid-state supercapacitors with superior performance in a 1 M H2SO4 electrolyte. The two-step process (involving ANS carbonization followed by activation) is found to significantly enhance specific surface area and total pore volume compared to a one-step process, reaching values of 2334 m(2)g(-1) and 1.21 cm(3)g(-1) versus 1394 m(2)g(-1) and 0.83 cm(3)g(-1), respectively. The superior surface area and pore volume results are achieved at a KOH/char mass ratio of 4:1, carbonization temperature of 500 degrees C, and an activation temperature of 800 degrees C, reaching 3091 m(2)g(-1) and 1.52 m(3)g(-1), respectively. Evaluation of electrochemical properties in a two-electrode system with 1 M H2SO4 electrolyte demonstrates outstanding capacitance and maximum specific energy at a current density of 125 mAg(-1), reaching up to 416 Fg(-1) and 14.5 Whkg(-1) at a specific power of similar to 120 Wkg(-1). This superior performance is attributed to the ACs' high surface area, well-developed microporosity, and favorable surface chemistry. Additionally, the ACs demonstrate exceptional cycling stability, as they retain 99 % of their specific capacitance even after undergoing 2500 charge and discharge cycles at a rate of 1 Ag(-1). This work offers a novel strategy for reclaiming Argan Nutshell, offering a sustainable approach for electrode materials in solid-state supercapacitors.