Upcycling Plastic Waste into Graphitic Carbon - Identifying the Roles of Oxygen Content and sp2 Extent in Graphene Forms: Complementary Tests with LDPE and PET

The proposed study seeks to upcycle consumer plastic waste into high value graphitic carbons for electric vehicles and renewable energy storage. Presently, petroleum and coal are the precursors for graphitic carbons used in Li-ion batteries. These sources are non-renewable and require substantial energy input for their processing. This research program will test the hypothesis that plastic waste constitutes a high-quality feedstock for graphene given its higher purity and uniformity compared to natural graphite. Upcycling waste plastic into high-value graphitic carbons will lead to improved recycling economics, increased recycling infrastructure investment, and growth of the recycling workforce while reducing greenhouse gas emissions and raising public awareness for recycling. This upcycling approach recovers the embodied energy cost of the plastic materials while trapping the carbon as a solid. As a new “resource,” plastic waste would eliminate petroleum and coal as feedstocks and displace mining for natural graphite. Upcycling plastic waste could transform the plastics recycling economy and thereby reduce plastic pollution, contributing to sustainability and adding a new path to a circular carbon economy. Outreach efforts include a) increasing diversity by summer internships for women in science and engineering research, b) promoting K-12 STEM through one-week science camps; and c) after-school events along with d) public dissemination via YouTube videos. The proposed study seeks to upcycle consumer plastic waste into high value graphitic carbons for electric vehicles and renewable energy storage. Low- and high-density polyethylene (LDPE, HDPE) and polyethylene terephthalate (PET) bracket the challenges of forming graphitic carbons from varied waste plastic feedstocks: high aliphatic (hydrogen) content (LDPE) and high oxygen content (PET). It is hypothesized that oxygen groups on graphene oxide (GO) can act as a substitute for the stabilization process required to promote carbonization over cracking reactions, while the 2D graphene sheet promotes ordered development of aromatic clusters during graphitization. Thermo-gravimetric analysis (TGA) will be used as a measure of stabilization effectiveness. Raman spectroscopy will quantify graphene lateral spacing La across the carbonization temperature range along with amorphous and molecular content to track carbonization progress. Polarized light microscopy (PLM) will visualize pre-graphitic domains, quantified by image analysis to be developed in this project. Wide angle X-ray scattering will gauge aromatic domain growth at pre-graphitic (pre-crystalline) stages. Upon emergence of graphitic structure, standard X-ray diffraction (XRD) will be used to determine crystal lattice parameters d002, La, Lc and graphitization index g. A sequence of experiments will be conducted to collectively characterize the level of graphitization with GO oxygen content and graphene (GR) sp2 area and peripheral length, to validate reactive force field (ReaxFF) molecular dynamics simulations. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) will provide localized measures of graphitic quality and microscopic uniformity at the nanoscale. Electrical conductivity will assess crystallite connectedness via impedance spectroscopy using a Randall circuit model. A potential implication of the GO stabilizer is that the rate of graphitization will increase, thereby realizing energy savings and CO2 reduction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.