Electron Irradiation of Graphene in Air at Atmospheric Pressure: a Method for Hydrogenating Graphene for Hydrogen Storage Applications

非技术性氢气储存是当前发展以氢为基础的绿色和可再生能源经济的一个重要议题。经过几十年的研究，氢还没有在汽车燃料电池等领域得到广泛的商业应用，主要是因为安全、经济和高效地储存氢的问题。在材料研究部固态和材料化学项目的支持下，北得克萨斯大学(UNT)的Jose Perez教授和他的研究小组将研究一种在大气压下使用电子辐照石墨烯来存储氢的简单、安全和商业可行的方法。常压下的石墨烯表面吸附了大量的水，被吸附的水的电子辐照可能会将水解离成氢，然后氢被吸附在石墨烯上；当石墨烯的温度上升到相对较低的200摄氏度时，吸附的氢就会解吸。主要目的是确定被吸附的物种是否是氢，并研究这种材料的存储、电学和光学性质。如果吸附的物种是氢，这可能会给储氢带来显著的好处。该项目将从代表性不足的群体中招募和培训本科生和研究生，并在当地高中组织展览和演示，以及在北卡罗来纳大学举办关于气候变化和可再生能源的科学博览会。技术总结该项目由材料研究部固体和材料化学计划支持，旨在研究石墨烯在接近大气压的空气中用1-30keV电子辐照后的性质。在此条件下辐照的机械剥离悬浮石墨烯的初步实验表明，拉曼D峰强度与拉曼G峰强度之比极高，为5.3，表明缺陷密度很高。以前关于负载型剥离石墨烯在真空中电子辐照的报道表明，产生的缺陷是氢吸附的。假设在近大气压力下照射的石墨烯中产生的缺陷也是氢吸附的，在这种情况下观察到的高缺陷密度可能意味着高氢覆盖率，将达到或超过能源部4.5wt%氢存储的目标。这种材料可以具有独特且有价值的储氢、机械、电学和光学性能。主要目的是确定辐照石墨烯中缺陷的身份和性质。本项目中使用的表征技术包括单个石墨烯样品的热解吸、标记质谱学、扫描隧道显微镜、拉曼光谱、原子力显微镜和X射线光电子能谱。该项目的外展活动包括在当地高中展示展览和演示，并为大都会地区的高中生组织一年一度的关于气候变化和绿色能源的科学博览会。该奖项反映了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 SUMMARYHydrogen storage is a topic of significant interest in the current development of a hydrogen-based energy economy that is green and renewable. After decades of research, hydrogen has not yet reached widespread commercial applications in areas such as vehicle fuel cells, mainly because of the problem of storing hydrogen safely, economically, and efficiently. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Professor Jose Perez and his research group at the University of North Texas (UNT) will investigate a method for storing hydrogen that is simple, safe, and commercially viable using electron irradiation of graphene at atmospheric pressure. Graphene at atmospheric pressure has a lot of water adsorbed on its surface, and electron irradiation of the adsorbed water may dissociate the water into hydrogen that then becomes adsorbed on the graphene; the adsorbed hydrogen desorbs when the temperature of the graphene increases to a relatively low temperature of about 200 degrees Celsius. The main objectives are to determine if the adsorbed species is hydrogen and investigate the storage, electrical and optical properties of this material. If the adsorbed species is hydrogen, this may bring significant benefits to hydrogen storage. The project will recruit and train undergraduate and graduate students from underrepresented groups and organize exhibits and demonstrations at local high schools and a science fair at UNT on climate change and renewable energy resources.TECHNICAL SUMMARYThis project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, aims to investigate the properties of graphene after irradiation with 1-30 keV electrons in air at near-atmospheric pressure. Preliminary experiments on mechanically exfoliated suspended graphene irradiated under such conditions show an extremely high ratio of the Raman D peak intensity to the Raman G peak intensity of 5.3, indicating a high defect density. Previous reports on electron irradiation of supported exfoliated graphene in a vacuum showed evidence that the defects produced are hydrogen adsorbates. Assuming the defects produced in graphene irradiated at near-atmospheric pressure are also hydrogen adsorbates, the high defect densities observed in this case may imply high hydrogen coverages that would meet or exceed the Department of Energy target of 4.5 wt % hydrogen storage. Such material may have unique and valuable hydrogen storage, mechanical, electrical, and optical properties. The primary objectives are to determine the identity and properties of the defects in the irradiated graphene. The characterization techniques used in this project are thermal desorption from individual graphene samples, labeled mass spectroscopy, scanning tunneling microscopy, Raman spectroscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. The outreach activities for this project include presenting exhibits and demonstrations at local high schools and organizing a yearly science fair for high school students in the Metroplex area on climate change and green energy.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.