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

Sci Total Environ. 2021 Jun 10:772:145309. doi: 10.1016/j.scitotenv.2021.145309. Epub 2021 Feb 2.

Abstract

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% CH4. After CO2 removal, the high caloric value of the pyrolysis gas could reach 29.2 MJ m-3, which could be used as a substitute natural gas. Pyrolytic carbon was further activated by KOH and ZnCl2. KOH-activated carbon (AC-K) obtained a hierarchical porous structure, a high specific surface area of 2683 m2 g-1 and abundant surface functional groups. Working as supercapacitor electrodes, AC-K exhibited an outstanding specific capacitance of 325 F g-1 at a current density of 0.5 A g-1. 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.

Keywords: Activated carbon; Methane-rich pyrolysis gas; Supercapacitor; Waste polyethylene terephthalate.