• • The PPy-PPCH3BO3-CC anode, derived from pomelo peel biochar activated with H3BO3 and modified with polypyrrole, achieved a charge transfer resistance (Rct) of 12.82 Ω, a 74.64% reduction compared to the unactivated PPy-PPC-CC electrode, and delivered a maximum power density of 478.03 mW·m−2, a 79.71% improvement, underscoring its potential for cost-effective, high-performance MFC anodes.
• • Addition of Scutellaria baicalensis extract as a natural electron mediator increased the maximum output voltage to (637±10) mV, power density to 586.68 mW·m−2, and Coulombic efficiency to (66.94±1.02)%, representing respective enhancements of 7.06%, 22.63%, and 21.95% over the control, while also prolonging high-voltage output duration, indicating superior electron shuttle capability.
• • In the combined system treating methyl orange wastewater, the maximum output voltage was (587±10) mV, power density 423.12 mW·m−2, Coulombic efficiency (57.85±1.06)%, and decolorization rate (95.86±1.12)%, with a 9.11%, 36.86%, 26.78%, and 5.63% improvement over the control, respectively, and a significantly reduced internal resistance of 7.15 Ω, demonstrating synergistic enhancement of electricity generation and dye degradation.
• • The use of pomelo peel, an abundant agricultural waste, as a precursor for high-performance biochar anodes, combined with plant-derived EMs, offers a sustainable and low-cost strategy to overcome the bottlenecks of expensive anode materials and synthetic mediators, aligning with green chemistry principles and circular economy goals.