Solvo/hydrothermal upcycling of polyethylene plastic-waste into carbon-based nanocomposite for supercapacitor application

One of the most worrying environmental issues affecting all forms of life, the economy, and natural ecosystems globally is the accumulation of polyethylene (PE) plastic garbage. Creating peaceful and environmentally friendly alternatives to conventional disposal techniques, like transforming plastic waste into cherished carbonaceous nanomaterials, is of utmost importance considering this threat. The current study carefully employed a cleaner upcycling technique to create carbon-based nanomaterials (CNMs) for supercapacitors. Using solvothermal/hydrothermal synthetic techniques, the PE waste was transformed into CNMs used in energy storage supercapacitors application. With an energy density of 21.6 W h kg−1 and a current density of 0.25 A g−1, the electrochemical test showed a specific capacitance of 155.5 F g−1. Additionally, the materials demonstrated 98.5% capacitance retention after 9000 cycles at a constant current density of 1.0 A g−1. Abbreviations: AC: activated carbon; CNM: carbon nanomaterials; CV: cyclic voltammetry; EC: electrochemical system; EDLC: electrical double layer capacitor; EIS: electrochemical impedance spectroscopy; FESEM: field emission scanning electron microscopy; FTIR: Fourier transform infrared; GCD: galvanostatic charge–discharge; HDPE: high-density polyethene; KOH: potassium hydroxide; LLDPE: linear low-density polyethene; Mn: manganese; PE: polyethene; Rct: charge transfer resistance; SSA: specific surface area; TEM: transmission electron microscopy; TGA: thermogravimetric analysis; UV–VIS: ultraviolet–visible spectroscopy; XRD: X-ray diffraction Highlights The article explored a low-temperature and non-emission upcycling method of polyethylene plastic waste into carbon-based nanomaterials (CNMs). CNMs were characterised for physical–chemical properties using different characterisation techniques. The carbon material was used with other materials like activated carbon and manganese to produce nanocomposites tested for electrical double layer capacitor energy storage and exhibited higher energy density.