Low-density polyethylene-derived carbon nanotubes from express packaging bags waste as electrode material for supercapacitors

A simple and efficient method for disposing of waste low-density polyethylene (LDPE) express packaging bags is proposed in this paper as a way to minimize waste and address the energy shortage at the same time. In addition to following the production of carbon nanotubes (CNTs) derived from LDPE, the application of CNTs as electrodes for supercapacitors was attempted. Waste LDPE bags were pyrolyzed and carbonized with catalyst using a dual-temperature reaction system, a designed 450 °C pyrolysis temperature accompany with different carbonization temperatures (650 °C, 700 °C, 750 °C, 800 °C, 850 °C), and treatment durations (0 h, 2 h, 4 h, 6 h) were investigated. As determined by FE-SEM and FE-TEM, the CNTs synthesized at 750 °C showed a finer tube diameter, much more uniform distribution, bamboo-like structure, as well as the highest yield of 41.9 %, and carbon conversion of 61.2 %. As being charged and discharged 10,000 times, the electrode remained a 93.16 % capacitance and a 92.85 % Coulomb efficiency. A dual-temperature reaction system could be utilized to recycle waste LDPE efficiently, and the LDPE-derived CNTs could be applied for supercapacitors.