Polyethylene waste carbons with a mesoporous network towards highly efficient supercapacitors

Herein, hierarchical porous carbon derived from polyethylene waste (plastic bags etc.) has been synthesized by ball-milling and carbonization with a flame-retardant agent, basic magnesium carbonate pentahydrate (MCHP:4MgCO₃·Mg(OH)₂·5H₂O). The presence of MCHP not only provides in-situ MgO template during pyrolysis, but also greatly enhances the thermal stability of polyethylene for carbonization. After subsequent NH₃ activation, the polyethylene waste derived carbon (PE-HPC-900NH₃) shows a high surface area and a unique property of meso-porosity, which contribute to the excellent capacitive performance. Remarkably, the obtained PE-HPC-900NH₃ electrode displays a relatively high specific capacitance with excellent cycling stability (about 97.1% of capacitance retention after 10,000 cycles at 2 A g⁻¹). A high energy density of 43 Wh kg⁻¹ can be achieved for the PE-HPC-900NH₃ symmetrical supercapacitor at an extremely wide voltage of 4 V in EMIMBF₄ due to the high purity and low ratio of O/N. This work provides a promising approach to disposal of waste plastics and opens new applications in various energy fields.