Unveiling the Electrochemical Versatility of N-Doped Porous Carbon in Aqueous and Redox Additive Electrolytes

Supercapacitors are prized for their high-power delivery, though their energy storage capacity is generally lower than that of batteries. A novel one-pot strategy for synthesizing nitrogen-doped porous carbon derived from KOH and urea-activated wheat bread waste (Triticum aestivum) is presented. This unique synthesis simultaneously achieves chemical activation and nitrogen doping in a single-step process, offering a cost-effective and scalable route for high-performance electrode materials. The supercapacitive properties of bread waste-derived activated carbon (BWC-700) in a 1 M H₂SO₄ aqueous electrolyte are investigated, with 0.01 M hydroquinone (HQ) acting as a redox-active agent. Morphological analysis via field-emission scanning electron microscopy confirms the material's hierarchical porous structure. The (BWC-700) exhibits a specific capacitance of 486 F g⁻¹ at a current density of 1 A g⁻¹ in a half-cell configuration, with specific capacities of 1422 C g⁻¹ and 904 C g⁻¹ in three- and two-electrode systems, respectively. When HQ is incorporated into the electrolyte, the AC demonstrates excellent cyclic stability, retaining 82% of its capacitance after 5000 cycles. Notably, BWC-700 achieves a peak energy density of 56.5 Wh kg⁻¹, outperforming symmetric supercapacitors. These findings underscore the novel combination of waste valorization, green synthesis, and redox-enhanced energy storage, making this work highly relevant and competitive in the rapidly evolving field of supercapacitors.