CAS: Green Graphitic Carbon from Natural Precursors Using Graphene Oxide Additives: A Combined Experimental and Atomistic Approach

石墨是绿色转型的关键原材料，并且在包括电动汽车和绿色能源存储在内的市场中的需求正在增加。根据目前的产量，除非找到新的来源，否则这些市场的需求将导致严重的供应短缺。不幸的是，石油衍生的石墨是不可再生资源，并且需要密集的能量来转化为石墨，而开采的石墨的供应是有限的，不足以满足不断增长的需求。相反，生物基资源（例如，来自造纸的木质素副产物、纤维素材料）是用于转化成石墨的可再生和可持续的前体，但是这些生物基前体含有促进非石墨化结构的氧。 通过该项目，在材料研究部的固态和材料化学计划的支持下，宾夕法尼亚州立大学的Randy Vander Wal和Adri货车Duin教授及其研究小组将探索一种称为反应性模板的生物基前体石墨化的创新工艺，其中氧化石墨烯添加剂和受控加热将能够形成所需的石墨晶体结构。 原子尺度的模拟将用于确定这种模板辅助转化为石墨的时间和温度限制。模板化转化还可以降低生物基材料转化为石墨所需的温度，节省能源，同时减少与制造相关的CO2排放。 该项目通过为宾夕法尼亚州立大学夏季举行的科学夏令营提供示范，并为课后活动开展科学参与活动，促进K-12 STEM。通过在学年期间接待一年级女大学生，该项目有助于STEM管道的多样性。为中学和中学后教育工作者编写的教材有助于劳动力发展。你管视频突出高温材料转化为石墨促进公众与研究的联系。该项目聘请了一位行业顾问，为项目提供基于市场的反馈。技术总结石墨碳因其低成本、高电导率、稳定的理化性能和长循环寿命而非常适合作为电池储能系统的电极材料。一种生物基、可再生和可持续的前体将取代目前用于制造用于能源储存的碳的石油或煤衍生化合物，同时减少与其生产相关的二氧化碳排放。该项目由材料研究部的固态和材料化学项目支持，研究了在生物聚合物中添加氧化石墨烯将碳结构从非石墨化重定向到高温处理阶段石墨化的假设。假设是生物聚合物基质自由基与氧化石墨烯上的那些自由基交联，而不是与其他生物聚合物定位的自由基交联，从而模板化到氧化石墨烯并在更高的热处理后形成石墨结构。 目标生物聚合物包括纤维素和提取的木质素，它们都是市售的。结构出现的时间尺度和温度由实验和原子尺度的模拟方法相结合来描述。反应性分子动力学模拟揭示了生物聚合物类型、GO上的O原子含量的潜在机理步骤和相对贡献，并在比实验可行的更宽的空间内探索反应参数（例如温度），从而为组分分数和元素含量提供进一步的实验指导。这项研究还有助于通过高分辨率透射电子显微镜（HRTEM）和原子模型模拟与导电性连接的碳石墨化动力学之间的第一个直接比较。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Non-technical summaryGraphite is a critical raw material for the green transition and demand is increasing in markets including electric vehicles and green energy storage. Based on current production, demand from these markets will result in a significant supply shortfall unless new sources are identified. Unfortunately, petroleum-derived graphite is a nonrenewable resource and requires intensive energy for conversion to graphite while the supply of mined graphite is limited and insufficient to meet the growing demand. In contrast, bio-based resources (e.g., the lignin byproduct from papermaking, cellulosic materials) are renewable and sustainable precursors for conversion into graphite but these bio-based precursors contain oxygen which fosters non-graphitizing structure. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Professors Randy Vander Wal and Adri van Duin and their research groups at Penn State University will explore an innovative process towards the graphitization of bio-based precursors called reactive templating in which graphene oxide additives and controlled heating will enable the formation of desired graphitic crystalline structure. Atomistic-scale simulations will be used to identify time and temperature constraints for this template-assisted conversion into graphite. The templated conversion may also lower the temperatures required for conversion of bio-based materials into graphite, saving energy while reducing CO2 emissions associated with the manufacturing. This project promotes K-12 STEM by contributing demonstrations to science camps held during summers at Penn State and developing science engagement activities for after-school events. By hosting first year women undergraduates during the academic year this project contributes to diversity in the STEM pipeline. Instructional materials for secondary and post-secondary educators contribute to workforce development. You tube videos highlighting the high temperature material conversion into graphite facilitates public connections with the research. Engagement of an industrial advisor on the project provides market-based feedback to the project.Technical summaryGraphitic carbons are ideally suited as electrode materials for battery-based energy storage systems given their low cost, high electrical conductivity, stable physicochemical properties, and long cycle life. A bio-based, renewable and sustainable precursor would displace the oil or coal derived compounds presently used in the manufacture of carbons for energy storage while reducing CO2 emissions associated with their production. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, investigates the hypothesis that the addition of graphene oxide to biopolymers redirects the carbon structure from non-graphitizing to graphitizing during high temperature treatment stages. The postulate is that the biopolymer matrix radicals cross-link with those on the graphene oxide, rather than with other biopolymer sited radicals, thereby templating to the graphene oxide and forming graphitic structure upon higher heat treatment. The targeted biopolymers include cellulose and extracted lignin, which are both commercially available. The timescales and temperatures over which structure emerges are delineated by a combined experimental and atomistic-scale simulation approach. Reactive molecular dynamics simulations reveal the underlying mechanistic steps and relative contributions of biopolymer type, O-atom content on GO, and explore reaction parameters such as temperature over a far broader space than experimentally feasible, therein providing further experimental guidance for component fractions and elemental contents. This study also contributes the first direct comparison between carbon graphitization kinetics via high resolution transmission electron microscopy (HRTEM) and atomistic model simulations—with connection to electrical conductivity.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.