Effect of Activating Agent and Temperature Conditions on the Electrochemical Performance of Rice Husk-Based Activated Carbon in Supercapacitors

This study investigates the electrochemical properties of activated carbon (AC) derived from rice husk, focusing on the influence of activation conditions using NaOH and KOH at temperatures of 650 °C, 750 °C, and 850 °C. The results demonstrate that RH-AC/KOH activated at 750 °C exhibits the highest capacitance retention (159‒165 F·g–1) and superior electrochemical performance, attributed to its optimized microporous structure and enhanced electrical conductivity. These properties make it an excellent candidate for electrode material in supercapacitors. Electrochemical evaluations, including cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS), confirm that RH-AC/KOH activated at 750 °C delivers the highest current density, stable performance across a wide voltage range (0.6‒1.5 V), and the longest discharge duration. A comparison of the specific current change (∆Sc) at low potentials (0.6‒1.0 V) for the four samples AC/NaOH at 850 °C and RH-AC/KOH at 750 °C, 650 °C, and 850 °C shows the following trend: 281.2 > 269.2 > 267.6 > 190.5 mA·g–1. At higher potentials (1.2–1.5 V), the ∆Sc values follow the order: 341.9 ≈ 340.0 > 314.6 > 247.8 mA·g–1. These findings identify RH-AC/KOH activated at 750 °C as a highly promising electrode material for next-generation supercapacitors, offering unique energy storage capacity, stability, and long-term durability.