Predictive design of biomass-derived biochar electrodes through quantitative structure-performance relationships

The circular bioeconomy promotes the conversion of renewable biomass into high-value materials for sustainable technologies. Biomass-derived biochar offers a compelling alternative as a tunable carbon material for electrochemical electrodes. However, predictive understanding of how intrinsic biochar properties govern electrochemical behavior remains limited. This study establishes a quantitative structure-performance framework linking biochar composition, surface morphology, and electronic structure to electron-transfer kinetics and signal output. Systematic physicochemical and electrochemical characterization of biochars from diverse biomass feedstocks, combined with correlation and regression analyses, revealed that interfacial roughness dominates kinetic resistance, with each 1 nm increase increasing ΔEp by ∼ 0.03 V and Rct by ∼ 493 Ω. Electrochemical activity was governed by electronic structure, where each 1% increase in sp 2 carbon content and each 1 µS/cm increase in bulk conductivity enhanced the anodic peak current ( i pa ) by ∼ 0.86 µA and ∼ 0.08 µA, respectively. Moreover, a large surface area (> 300 m 2 /g) with a disordered carbon framework is known to suppress charge transport. These findings deliver quantitative design rules for rational feedstock selection and pyrolysis optimization, demonstrating the transformation of agricultural residues for application in high-performance electrochemical carbon materials.