Biomass-derived activated carbon/MXene composites as supercapacitor electrodes

Sustainable and high-performance electrode materials derived from agricultural waste are highly desirable for next-generation supercapacitors. In this work, activated carbons were synthesized from rice husks, walnut shells, and apricot shells via carbonization followed by KOH chemical activation. The obtained biomass-derived carbons exhibit high specific surface areas and well-developed porous structures; however, their electrochemical behavior is strongly governed by pore architecture and structural stability. Among the investigated materials, rice husk-derived activated carbon (RHAC) demonstrates the most stable electrochemical performance, benefiting from its hierarchical micro-mesoporous structure and robust carbon framework. To further enhance the electrochemical properties, RHAC was composited with MXene at different mass ratios (50:50, 60:40, and 70:30). The optimized RHAC/MXene (60:40) electrode delivers a high specific capacitance of ∼255 F/g at 100 mA/g, corresponding to an energy density of ∼35 Wh/kg at a power density of ∼500 W/kg and maintains ∼160 F/g at 2000 mA/g, demonstrating excellent rate capability. In addition, the electrode shows superior cycling stability with ∼85–90% capacitance retention after 10,000 cycles. The enhanced electrochemical performance is attributed to the synergistic interaction between the stable porous RHAC framework and the highly conductive MXene network, enabling efficient ion transport and rapid electron transfer. Overall, this study highlights rice husk-derived activated carbon as a promising and sustainable carbon matrix for MXene-based supercapacitor electrodes and provides valuable insights into the rational design of biomass-derived hybrid materials for advanced energy storage applications.