Green conversion of waste polyethylene terephthalate to functional porous carbon: Mg/Ni synergistic modulation for enhanced supercapacitive energy storage.

To realize high-value recycling of polyethylene terephthalate (PET) and fabricate high-performance supercapacitor carbon electrodes, a Mg/Ni mono- and co-doping regulation strategy is proposed. Three carbon materials (PAC-Mg, PAC-Ni, and PAC-NiMg, where PAC denotes porous activated carbon) were prepared from PET powder via KOH activation, and their microstructures and electrochemical properties were systematically investigated. Among them, Mg dominates pore formation, giving PAC-Mg a specific surface area of 1583.16 m2 g-1, while Ni promotes locally enhanced graphitic ordering and improved electronic conductivity in PAC-Ni. The Mg/Ni co-doping carbon-based material achieves synergistic optimization of porosity and conductivity, with PAC-NiMg retaining 69.87% capacitance at 6 A g-1 under a three-electrode configuration. In 0-1.7 V asymmetric supercapacitors (PAC negative, Ni(OH)2 positive), Ni(OH)2//PAC-Ni delivers 159.76 F g-1 and 64.13 Wh kg-1 at 1 A g-1, while Ni(OH)2//PAC-NiMg exhibits 29.61 Wh kg-1 at 6 A g-1 with excellent rate capability. This work provides a new approach for PET upcycling and experimental evidence for metal doping-regulated structure-performance relationships of carbon materials.