Engineering biomass heterogeneity of puffed rice into optimal pore topology for high-performance supercapacitors

Abstract

Rational pore architecture—featuring optimal size distribution, interconnected frameworks, and maximized accessible surface area—is critical to achieve high energy density without compromising power density. Biomass-derived porous carbons are known for their natural hierarchical porosity, self-doped heteroatoms, cost-effectiveness, and sustainability, yet suffering from unbalanced macro-/micro-pore ratios and unresolved template-activation tradeoffs. Herein, we report a puffed rice-derived three-dimensional honeycomb-like hierarchical porous carbon (HPC) via synergistic KOH activation and MnO sacrificial templating, producing an interconnected porous network with an ultrahigh specific surface area (3107 m² g⁻¹) and optimized ion transport pathways. The HPC delivers capacitances as high as 676 F g⁻¹ (1 A g⁻¹, three-electrode) and 409 F g⁻¹ (0.1 A g⁻¹, two-electrode) in 6 M KOH, with outstanding rate capability (75.3 % retention at 10 A g⁻¹) and cycling stability (93.7 % retention after 100,000 cycles). As a symmetric supercapacitor using EMIMBF₄ electrolyte, HPC achieves 123.8 Wh kg⁻¹ at 450 W kg⁻¹ and retains 104 Wh kg⁻¹ even at 12,600 W kg⁻¹. This work represents a paradigm shift in biomass utilization by converting inherent biological heterogeneity into a structural advantage through controlled pore engineering.