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

这项拟议的研究旨在将消费塑料垃圾升级为高价值的石墨碳，用于电动汽车和可再生能源储存。目前，石油和煤是锂离子电池中石墨碳的前驱体。这些来源是不可再生的，需要大量的能源投入来处理。与天然石墨相比，塑料垃圾具有更高的纯度和均匀性，因此该研究计划将测试塑料垃圾构成石墨烯高质量原料的假设。将废塑料升级为高价值的石墨碳将改善回收经济，增加回收基础设施投资，增加回收劳动力，同时减少温室气体排放，提高公众对回收的认识。这种升级回收方法回收了塑料材料的隐含能源成本，同时将碳作为固体捕获。作为一种新的“资源”，塑料垃圾将取代石油和煤炭作为原料，并取代天然石墨的开采。塑料垃圾的升级回收可以改变塑料循环经济，从而减少塑料污染，有助于可持续发展，并为循环碳经济增加一条新的途径。拓展工作包括：a)通过为科学和工程研究领域的女性提供暑期实习来增加多样性；b)通过为期一周的科学营推广K-12 STEM；c)课后活动以及d)通过YouTube视频向公众传播。这项拟议的研究旨在将消费塑料垃圾升级为高价值的石墨碳，用于电动汽车和可再生能源储存。低和高密度聚乙烯（LDPE， HDPE）和聚对苯二甲酸乙二醇酯（PET）克服了从各种废塑料原料（高脂肪（氢）含量（LDPE）和高氧含量（PET））形成石墨碳的挑战。假设氧化石墨烯（GO）上的氧基可以替代催化裂化反应所需的稳定过程，而二维石墨烯片在石墨化过程中促进芳香团簇的有序发展。热重分析（TGA）将被用作稳定效果的测量。拉曼光谱将量化石墨烯在碳化温度范围内的横向间距La以及非晶和分子含量，以跟踪碳化进展。偏振光显微镜（PLM）将可视化预石墨畴，通过本项目中开发的图像分析进行量化。广角x射线散射将测量在预石墨（预结晶）阶段芳畴的生长。在石墨结构出现后，将使用标准x射线衍射（XRD）来确定晶格参数d002， La， Lc和石墨化指数g。将进行一系列实验，通过氧化石墨烯氧含量，石墨烯（GR） sp2面积和外围长度来共同表征石墨化水平，以验证反应力场（ReaxFF）分子动力学模拟。透射电子显微镜（TEM）和选择区域电子衍射（SAED）将在纳米尺度上提供石墨质量和微观均匀性的局部测量。电导率将通过使用兰德尔电路模型的阻抗谱来评估晶体的连通性。氧化石墨烯稳定剂的一个潜在意义是，石墨化的速度将会增加，从而实现节能和减少二氧化碳。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.