<p>The extensive use of highly corrosive alkali in the production of biomass-derived porous carbon has led to environmental pollution and equipment degradation. This study effectively combined the Fenton-liked reaction with doping techniques and employed a mild alkali activation method to successfully prepare hierarchical porous biomass carbon materials with a specific surface area of 2019.12 m g⁻¹. The specific capacitance of the prepared carbon electrode was 307.9 F g⁻¹, which was a significant improvement over the capacitance obtained by conventional activation methods. Additionally, the assembled symmetric supercapacitor exhibited a capacitance retention of 93.75% after 10,000 charge/discharge cycles at 5 A g⁻¹. It achieved a maximum power density of 0.81 kW&#xa0;kg⁻¹ at an energy density of 18.2 Wh kg⁻¹. These promising capacitive properties suggested that the combination of Fenton chemistry and nitrogen doping could have broader applications for developing other biomass-based electrode materials.</p>