Enhanced Supercapacitance Performance of Hierarchically Porous Carbon Obtained from <i>Terminalia bellirica</i> (Barro) Seed Stone

Biomass carbons are promising candidates for energy storage applications due to their large surface areas, hierarchical pore structures, well-defined pore dimensions, and tunable porosity. Here, we report the production of porous carbon materials from Terminalia bellirica (Barro) seeds involving zinc chloride activation at different impregnation ratios (1:1–1:3) and carbonization temperatures (700–900 °C), and their supercapacitive performances in 1 M sulfuric acid in three-electrode and two-electrode systems. The material carbonized at 700 °C at an impregnation ratio of 1:3 exhibited a high specific surface area of 2301 m2·g–1 and a large pore volume of 1.887 cm3·g–1. Electrochemical analyses revealed an electrical double-layer charge storage mechanism, and the electrode achieved a maximum specific capacitance of 365.4 F·g–1 at 1 A·g–1 with an excellent capacitance retention of 66.0% even at 50 A·g–1. The symmetric supercapacitor cell assembled using this material delivered an energy density of 7.1 W·h kg–1 at a power density of 600 W·kg–1 retaining 98.2% cycle life after 10,000 charge/discharge cycles. These results indicate that there is great potential in using Barro seed as a sustainable carbon source for the fabrication of high surface area activated carbons for energy storage supercapacitor applications.