Novel biomass enhances supercapacitor performance by precisely controlling pore structure, nitrogen/oxygen (N/O) atom content, and functional group distribution

Abstract

s The demand for sustainable energy storage solutions continues to grow. As an agricultural waste, Bertholletia excelsa Bonpl. (BEB) Shells can be converted into electrode materials, reducing environmental pollution while enhancing economic value. This study elucidates the synergistic regulation mechanism among pore structure, heteroatom（N 0.81 %， O 5.28 %), and functional group content, resolving their competitive interactions. Adjusting the KOH ratio disrupts the inter-crosslinked macromolecular structures in biomass, generating abundant micropores (2057m² g - ¹) and mesopores ( 60.2m² g - ¹). The increased micropore density exposes more NO active sites, promoting their loss at high temperatures. This process alters the relative content of surface functional groups on the biomass . Precise regulation of BEB's pore structure, heteroatom, and functional group contents yields carbon materials with outstanding electrochemical performance(PC-3): a high specific surface area (2450 m² g⁻¹), excellent specific capacitance (327 F g⁻¹ at 0.5 A g⁻¹), and remarkable cycling stability (99.4 % retention after 10,000 cycles). The particular capacitance exceeds that of PC-1 (176 F g⁻¹), PC-2 (208 F g⁻¹), and PC-4 (276 F g⁻¹). The assembled symmetric supercapacitor demonstrates 87 % capacity retention after 4000 cycles. PC-3 demonstrates a K⁺ adsorption energy of −1.58 eV. DFT calculations reveal that under optimized specific surface area conditions, NO atoms and functional groups synergistically enhance electrolyte ion adsorption and storage capacity. This optimizes between specific surface area and heteroatom/functional group content. This study provides systematic theoretical guidance for designing pore structures and heteroatom doping strategies in biomass-derived carbon materials.

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