Abstract Here, hemp sawdust waste was converted into high‐performance activated carbons through chemical activation and targeted heteroatom doping. Nitrogen, sulfur, and phosphorus were introduced individually (NAC, SAC, PAC) and in combination (NSPAC) to tailor porosity and surface chemistry. Remarkably, the obtained carbons exhibited high specific surface areas (up to 3456 m 2 /g), comparable to or exceeding many reported biomass‐derived heteroatom‐doped carbons, highlighting the effectiveness of this approach. The materials were evaluated as symmetric two‐electrode supercapacitors in aqueous electrolyte within a 0–0.8 V window using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. All electrodes exhibited quasi‐rectangular CVs and linear, symmetric GCD curves, indicating electric double‐layer storage with mild pseudocapacitive contributions in the doped samples. A consistent performance hierarchy was observed: NAC delivered the highest response, closely followed by NSPAC, while AC and PAC maintained highly reversible behavior with strong rate capability, and SAC showed comparatively lower performance due to reduced internal surface area and higher interfacial resistance. Impedance analysis linked high‐rate operation to low charge‐transfer resistance, explaining the PAC–AC crossover at the highest current. Long‐term cycling over 10,000 cycles retained more than 95% of the capacitance, clearly demonstrating durability. These findings establish a robust structure–property relationship: accessible hierarchical porosity combined with carefully designed heteroatom chemistry enables sustainable electrodes with high capacitance, strong rate performance, and excellent stability. Hemp waste, therefore, represents a scalable feedstock for aqueous supercapacitors, offering both low cost and practical applicability.
Inal et al. (Fri,) studied this question.