University of Texas At Austin
Grant: $633,687 - National Science Foundation - May. 22, 2009
50% voted satisfied - 50% voted not satisfied - 4 vote(s) cast
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Award Description: The research objective of this award is to advance the manufacture, the fundamental understanding, and the device application of graphene-nanocrystal metamaterials or hybrid graphene-nanocrystal structures, i.e., graphene sheets with discrete nanocrystals decorations on their surfaces. Specific tasks to be performed include experimental and theoretical characterization of the metamaterials, particularly electronic and physical interactions between nanocrystals and graphene sheets with various external stimuli; investigation of methods for low-cost and large-scale manufacturing of such materials; and exploration of their use for gas sensors. The availability of affordable hybrid nanostructures and their fundamental properties will open up new opportunities for nanoscience and nanotechnology and accelerate discoveries and inventions. The synergistic response from the nanocrystal and the graphene can be harnessed for various innovative device applications, including gas sensors, biosensors, and photovoltaic cells. If successful, the project results will enable a wide range of innovative applications of graphene-nanocrystal metamaterials with optimal properties that can be tailored for specific conditions. The new sensor to be demonstrated will be attractive for environmental monitoring and directly benefit society. The project will train both graduate and undergraduate students in areas of graphene engineering and applications, and will reach the broader student population through a course module on hybrid nanostructures, integration of small nanotechnology projects into existing curricula at both UWM and UT, and training of science teachers. Additional efforts through 'Science Saturdays' will be used to attract more underrepresented students to STEM fields.
Project Description: One of the primary purposes of the award is to develop graphene-based ultracapacitors that utilize novel ionic liquids (ILs) as the electrolyte. Our preliminary data indicate that pyrrolidinium, piperidinium, and other ammonium-based ILs have very broad electrochemical windows, with those containing triflate anions showing the most promising results in terms of chemical stability (PF6 salts have comparable windows but tend to hydrolyze upon exposure to water). As a part of the proposed research, we plan to investigate other classes of anions to improve performance even further. In addition, we have found that mixing the aforementioned ILs with approximately 10 wt% of acetonitrile is sufficient to liquefy the ILs, which tend to be tacky solids at room temperature. Though this has the deleterious effect of diluting the electrolyte, it greatly decreases the viscosity of the mixture, and decreases the melting point of the mixture essentially to that of the solvent (-45 °C). This should provide far greater ion mobility, allowing for faster and more efficient charging/discharging of the ultracapacitor. Ultracapacitors fabricated from graphene and 1:1 mixtures of pyrrolidinium triflates in acetonitrile show excellent capacitive properties, giving an overall specific capacitance in excess of 120 F g-1. The electrochemical windows achieved in triflate-based systems are as good, or better, than all reported ultracapacitor devices of which we are aware, and the synthetic approaches toward fabrication of the ILs are straightforward. The state of the art appears to be a recently reported device that uses a pyrrolidinium-NTf2 system and achieves a window of approximately 3.7 V at temperatures ranging from -30 °C to 60 °C. We believe our systems have some key advantages that allow us to match or exceed this benchmark. Our immediate goal is to optimize the system in terms of the thermal and electrochemical properties of the IL in order to develop commercially viable devices.
Jobs Summary: A gradaute research asssistant was appointed .16 FTE. Calculations of Number of Jobs were made using OMB guidance. (Total jobs reported: 0)
Project Status: Less Than 50% Completed
This award's data was last updated on May. 22, 2009. Help expand these official descriptions using the wiki below.
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