<p>The rising global energy demand necessitates the development of efficient, cost-effective and sustainable strategies for energy storage systems. In the present work, activated carbon was synthesized from Diospyros melanoxylon’s fruit peel, a biomass waste and its performance in high-performance supercapacitors was explored for the first time. The activated carbon electrode derived from biomass (Diospyros melanoxylon’s fruit peel) exhibited an outstanding specific capacitance of 441.43 Fg^− 1 (at 0.5 Ag^− 1), as assessed in a three-electrode electrochemical setup. Structural characterization using FESEM and BET analyses confirmed the formation of a well-developed porous architecture in the synthesized activated carbon. The symmetric supercapacitor device delivered a specific capacitance of 138.48 Fg^− 1 (at 0.5 Ag^− 1) and exhibited excellent electrochemical performance, achieving a high power density of 10,000 Wkg^− 1 at an energy density of 12.50 Whkg^− 1. The symmetric supercapacitor device displayed 100% capacitance retention over 10,000 charge-discharge cycles in a 1 M H₂SO₄ electrolyte, representing good cycling stability and long-term durability. Furthermore, the symmetric supercapacitor device demonstrated a high rate capability of 93.83% at 1 Ag^− 1, along with a high coulombic efficiency of 93.30% at 1 Ag^− 1. Overall, these findings underscore the significant potential of <i>Diospyros melanoxylon</i>-derived activated carbon as a sustainable and high-performance electrode material for next-generation supercapacitor applications.</p> Graphical abstract <p></p>