| AVS 58th Annual International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Thursday Sessions |
| Session EN+NS-ThM |
| Session: | Nanostructures for Energy Storage and Fuel Cells I |
| Presenter: | Dan R. Dreyer, The University of Texas at Austin |
| Authors: | M. Acik, The University of Texas at Dallas D.R. Dreyer, The University of Texas at Austin C. Bielawski, The University of Texas at Austin Y.J. Chabal, The University of Texas at Dallas |
| Correspondent: | Click to Email |
One of a real-world application of Electrochemical Double Layer Capacitors (EDLCs) is their use in prototype electric vehicles. An EDLC simply consists of two non-reactive, porous electrodes and an electrolyte separated with a membrane. Activated charcoals are one of a commonly used electrode systems which has drawbacks such as limited energy storage due to their large ion size. Therefore, a replacement electrode system with a higher surface area is necessary for a superior EDLC performance. Modified graphene is one of a promising candidate with its high theoretical surface area (2630 m2/g). EDLC working principle also depends on how effectively it can polarize the electrolyte solution. In principle, ionic liquids are promising electrolyte systems with their high non‑volatility, non-flammability, thermal stability and good solvating ability.
This study focuses on the intercalation studies of ionic liquids such as N-methyl-N,N,N-tris(2-hydroxyethyl)ammonium iodide, N-methyl-N,N,N-tris(2-hydroxyethyl)ammoniummethyl sulfate, 1-butyl-3-methylimidazoliumemethylsulfate and N-octyl-N-methylpiperidinium methylsulfate. To achieve a high surface area material with modified graphene, it is essential to understand the interfacial interactions upon intercalation of ionic liquids.
We study powder X-Ray Diffraction Analysis to characterize the interlayer distance of modified graphene. For instance, its d-spacing increases by about 4-12 Å after intercalating as-synthesized graphite oxide (GO, ~9Å) with N-methyl-N,N,N-tris(2-hydroxyethyl)ammonium methylsulfate (IL) at room temperature. Annealing at 300-500°C, (002) orientation of GO disappears as a result of thermal exfoliation. In addition, in-situ Infrared Absorption Spectroscopy (IRAS) measurements were performed to explore the intercalation chemistry of modified graphene in the presence of ionic liquids. Therefore, we perform thermal reduction studies in vacuum coupled with IRAS measurements to characterize the chemical interactions during thermal exfoliation of reduced GO. After annealing GO intercalated with this IL, the loss of C-N and C-O containing species is identified at ~1000-1500 cm-1 and 800-1200 cm-1 with contribution from C-OH groups at 3000-3700 cm-1. Complete removal of these species is observed after a ~500°C anneal resulting in a weak infrared absorbance intensity of sp2-hybridized C=C species at ~1580 cm-1. The presence of new formation of sheet-to-sheet linking or bonding motifs was also studied with X-ray Photoelectron Spectroscopy (XPS).
*Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC001951.