Graphene triggered catalytic attack on plastic waste produces graphitic shell encapsulation on cobalt nanoparticles for ferromagnetism and stable Li+ ion storage

Abstract

Plastic materials, viz., Ziploc bags (polyethylene) and packing foam (polystyrene) produce graphitic shell encapsulated cobalt nanoparticles by catalytic microwave deconstruction in 2 minutes. The phase purity is confirmed as cubic crystalline, having graphitic carbon with core–shell architecture recognized by a D-band at 1330 cm⁻¹ and G-band at 1575 cm⁻¹, attributed to the calculated specific surface area of 39 m² g⁻¹ for Co-GNP-ZipC, 19 m² g⁻¹ for Co-GNP-FmC and 47 m² g⁻¹ for pristine Co-GNP. Transmission electron microscopic results reveal graphitic shell encapsulation, 20 nm cobalt nanoparticles, carbon lattice fringes, and crystalline cobalt's ring patterns having bright diffraction spots. The magnetization M vs. H and magnetic susceptibility χ vs. T of pristine Co-GNP, Co-GNP-ZipC, and Co-GNP-FmC materials show the ferromagnetism of cobalt nanoparticles. Kinetic studies of the graphitic core–shell architecture exhibit an additional charge storage buildup and three reversible redox peaks, attributed to (de)insertion in the trace amount of amorphous CoO, conversion reaction of CoO to Co and Li₂O and Li⁺ ion (de)intercalation in graphitic shell encapsulated carbon. The plastic waste-derived composite materials deliver a reversible capacity of 377 mA h g⁻¹ for Co-GNP-ZipC and 509 mA h g⁻¹ for Co-GNP-FmC at the 250th cycle compared to the pristine Co-GNP material (<1 mA h g⁻¹), as a superior Li⁺ ion storage material.