Waste Plastic‐Derived FeMo@MgO/CNTs Nanocomposites for High‐Performance Supercapacitor Applications

Abstract Multiwalled carbon nanotubes (MWCNTs) were prepared from low‐density polyethylene (LDPE) plastic waste using FeMo(x)@MgO catalysts with several FeMo contents (x=10, 30, and 50 %). Pyrolysis of waste LDPE and growth of CNTs over FeMo/MgO catalysts were performed at 450 and 750 °C, respectively. The results indicated that FeMoO 4 , Fe 2 (MoO 4 ) 3 , MgFe 2 O 4 , MgMoO 4 , and Mg 2 Mo 3 O 11 species were the main components of the calcined catalyst containing 50 %FeMo. However, free monometallic iron oxides and bimetallic oxides (MgFe 2 O 4 , and MgMoO 4 ) were the components of the calcined catalyst containing 10 %FeMo. The FeMo content was found to correlate with the yield and quality of the carbon product. TEM images of the spent catalysts proved the formation of MWCNTs at all FeMo contents. The FeMo(30)/MgO catalyst was the most active in CNT production. Raman spectroscopy results proved the generation of the best quality MWCNTs at 30 %FeMo content. XRD analysis of the spent catalysts demonstrated that nanocomposite of Fe 3 C, Mo 2 C, MgO, and MWCNTs (FeMoC(x)@MgO/CNTs) was successfully synthesized. The electrochemical performance of FeMoC(x)@MgO/CNTs composites was evaluated as low‐cost supercapacitor nanoelectrodes. Large specific capacity values of 806, 978, and 1180 F g were achieved at the current density of 0.1 A g using nanocomposites with 10, 30, and 50 %FeMo contents, respectively.