Molten base carbonisation and activation of non-lignin-rich biomass into hierarchically porous carbon with surface-rich functionalities for supercapacitor electrodes

Non-lignin-rich biomass has abundant reserves but remains underutilised as a sustainable carbon source for producing functional carbon materials in energy storage applications. The primary challenge is to develop an efficient and sustainable process to convert these resources into high-performance carbon as electrode active material for supercapacitors. To address this issue, a facile, low-cost molten base carbonisation and activation (MBCA) process is investigated to convert wet Radish (a non-lignin–rich biomass) into hierarchical porous carbon via a single thermal stage. This approach integrates carbonisation, in-situ activation, and heteroatom retention, yielding carbon with a specific surface area of 1172 m² g⁻¹, ultramicropores (0–0.7 nm), partial graphitic structure and nitrogen/oxygen-rich functional groups. The optimised carbon, obtained at 700 ˚C, as a supercapacitor electrode active material exhibited electrochemical performance, with a specific capacitance of 257F g⁻¹ at 5 mV s⁻¹ and 96F g⁻¹ at 2 A g⁻¹, alongside remarkable cycle stability (92.6 % capacitance retention over 20,000 cycles) and low self voltage decay over 50 h. These results highlight the MBCA process as a viable solution for converting non-lignin-rich biomass into high-performance carbon materials, offering a practical and sustainable alternative for energy storage applications while mitigating environmental pollution from biomass decomposition.