Sustainable Biomass-Derived Activated Carbons for Supercapacitors: Tailoring Porosity and Surface Chemistry for Enhanced Energy Storage

Supercapacitors (SCs) offer high power density, rapid charge-discharge capability, and excellent cycling stability; however, their relatively low energy density remains a major limitation for applications requiring sustained energy delivery. Biomass-derived activated carbons have emerged as sustainable, low-cost, and renewable alternatives to conventional carbon electrodes owing to their tunable porous structures and surface chemistry. This review critically analyzes recent advances in biomass-derived activated carbons, with particular emphasis on the synergistic effects of pore architecture and surface chemistry on electrochemical performance. Analysis of the available literature demonstrates that the electrochemical performance of biomass-derived carbons is not governed by specific surface area alone but by pore accessibility and the balance between ultramicropores for charge storage and mesopores for rapid ion transport. Consequently, reported specific capacitances range from approximately 100 to over 600 F g−1, depending on the biomass precursor and synthesis strategy. Furthermore, heteroatom doping, particularly with N, B, S, P, and co-doping strategies, significantly enhances electrical conductivity, electrolyte wettability, charge-transfer kinetics, and pseudocapacitive contributions. Representative studies show that nitrogen doping can nearly double the specific capacitance (e.g., from 178 to 324 F g−1) by improving interfacial electrochemical processes. The present review establishes an integrated structure-property-performance framework linking biomass precursor selection, activation strategy, pore architecture, surface functionality, and electrolyte compatibility, thereby providing practical design guidelines for the rational development of next-generation sustainable supercapacitor electrodes.