Green synthesis of Kenaf-based activated carbons with excellent rate capability and cycle-life via hydrothermal-co-activation process for high-performance capacitive energy storage

The invention of high-performance electrode materials through a simple and green approach is always important for energy storage applications. Herein, we have prepared highly porous activated carbons (ACs) from biomass kenaf (KF) by hydrothermal and steam activation methods. A number of optimization experiments, such as hydrothermal pre-treatment (100, 150 and 200 °C), steam activation temperature (600, 700, 800, and 900 °C) and time of steam flow (15, 30, 60 and 90 min) were performed to control the specific surface area, micro- and/or meso-pores, total pore volume for an excellent electrochemical performance. The as-obtained porous ACs exhibited a high specific surface area (∼1733 m²/g) with high total pore volume (∼0.916 cm³/g) and high mesopore volume (∼28.4%), which are beneficial for the excellent double layer formation over the surface of activated electrode and also provide transport channel for an effective diffusion of electrolyte ions. The as-derived ACs were used as electrode materials for the fabrication of symmetric supercapacitor device in 6 M KOH. The fabricated device exhibited a high energy density of 4.86 Wh kg⁻¹ at power density of 2500 W kg⁻¹ with outstanding stability (∼96.3%) over 10,000 charge-discharge cycles.