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

非技术概述石墨是绿色过渡的关键原材料，在包括电动汽车和绿色能源储存在内的市场上，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，石油石墨是一种不可再生的资源，需要密集的能源才能转化为石墨，而开采出的石墨供应有限，不足以满足日益增长的需求。相比之下，生物基资源(例如，造纸副产品木质素、纤维素材料)是可再生和可持续的转化为石墨的前体，但这些生物基前驱体含有氧，这促进了非石墨化结构。在材料研究部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教授和Adri van Duin教授及其研究小组将探索一种名为反应模板的生物前驱体石墨化的创新工艺，在该工艺中，石墨烯氧化物添加剂和受控加热将能够形成所需的石墨体晶体结构。原子级模拟将被用来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将生物基材料转化为石墨所需的温度，从而节省能源，同时减少与制造相关的二氧化碳排放。该项目通过为宾夕法尼亚州立大学夏季举办的科学夏令营提供示范，并为课外活动开展科学参与活动来促进K-12 STEM。通过在学年招收一年级女本科生，该项目有助于STEM渠道的多样性。为中学和中学后教育工作者编写的教材有助于劳动力的发展。You Tube视频突出了高温材料转化为石墨的过程，促进了公众与研究的联系。聘请工业顾问参与该项目，为项目提供基于市场的反馈。技术摘要石墨碳具有低成本、高导电性、稳定的物理化学性质和较长的循环寿命，非常适合用作基于电池的储能系统的电极材料。一种基于生物的、可再生的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炭衍生化合物，同时减少与其生产相关的二氧化碳排放。该项目在材料研究部固态和材料化学计划的支持下，研究了在高温处理阶段向生物聚合物中添加石墨烯氧化物将碳结构从非石墨化重定向到石墨化的假设。假设是生物聚合物基质自由基与氧化石墨烯上的自由基交联，而不是与其他生物聚合物定位于自由基，从而模板化到氧化石墨烯上，并在较高的热处理后形成石墨化结构。目标生物聚合物包括纤维素和提取木质素，这两种都是商业上可以买到的。通过实验和原子尺度模拟相结合的方法描绘了结构出现的时间尺度和温度。反应分子动力学模拟揭示了生物聚合物类型、O原子含量对GO的潜在机理步骤和相对贡献，并探索了温度等反应参数在远比实验可行的更广阔的空间上，其中为进一步的组份组成和元素含量提供了实验指导。这项研究还首次通过高分辨率电子显微镜(HRTEM)和原子模型模拟对碳石墨化动力学进行了直接比较-与电导率有关。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.