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

University Of North Texas, Denton TX

Investigators

Abstract

NON-TECHNICAL SUMMARY Hydrogen 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 SUMMARY This 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.