Upcycling of PET waste into methane-rich gas and hierarchical porous carbon for high-performance supercapacitor by autogenic pressure pyrolysis and activation.

The explosive growth of polyethylene terephthalate (PET) wastes has brought serious pollution to the environment. Here, PET waste was upcycled into methane-rich pyrolysis gas and carbon material for energy storage through autogenic pressure pyrolysis and post-activation. The pyrolysis gas contained 34.58 ± 0.23 vol% CH. After CO removal, the high caloric value of the pyrolysis gas could reach 29.2 MJ m, which could be used as a substitute natural gas. Pyrolytic carbon was further activated by KOH and ZnCl. KOH-activated carbon (AC-K) obtained a hierarchical porous structure, a high specific surface area of 2683 m g and abundant surface functional groups. Working as supercapacitor electrodes, AC-K exhibited an outstanding specific capacitance of 325 F g at a current density of 0.5 A g. After 5000 charge-discharge cycles, AC-K still retained 91.86% of the initial specific capacitance. This study provides a sustainable way to control plastic-derived pollution and alleviate the energy crisis.