| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Monday Sessions |
| Session GR+NS-MoA |
| Session: | Graphene: Chemical Reactions |
| Presenter: | M. Acik, University of Texas at Dallas |
| Authors: | M. Acik, University of Texas at Dallas C. Mattevi, Imperial College London C. Gong, University of Texas at Dallas G. Lee, University of Texas at Dallas K.J. Cho, University of Texas at Dallas M. Chhowalla, Imperial College London Y.J. Chabal, University of Texas at Dallas |
| Correspondent: | Click to Email |
Graphene/graphite oxide (GO), with its non-stoichiometric chemical structure and highly hygroscopic functionalized graphene backbone, has been of interest for chemical energy storage applications such as supercapacitors and ultracapacitors as well as its reduced form for bioelectronic applications such as sensor networks and for printed electronics. For all these applications, it is important to characterize and control the chemical nature of GO at various stages of thermal reduction. In particular, the formation and evolution of defect structures within GO can greatly impact the resulting properties. Similarly, the properties of species intercalated between individual planes can alter the reduction chemistry. The interplay between intercalated species and defect sites can lead to interesting new chemistry.
To understand these chemical interactions, we have studied the deoxygenation process of both single- and multi-layer(s) of GO and focused on comparing the removal of oxygen upon heating both from the basal plane and the edges, by bringing to bear a number of methods. In particular, we have carried out a series of experiments using in-situ IR absorption spectroscopy (FTIR), x-ray diffraction technique (XRD), ex-situ raman scattering, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS), together with density functional (DFT) calculations and molecular dynamic (MD) simulations of various oxygen structures and resulting electronic states. The IR absorption spectra reveal the formation of ketones, ethers and sp2-hybridized C=C as well as a loss of hydroxyls, carboxyls and epoxides upon gradual annealing. They also confirm that defect formation is a direct result of CO2 and CO formation, and highlight the role of intercalated species, such as water. At higher temperatures (~850⁰C), oxygen is found to remain at the edges of defective sites in a very stable configuration, involving the alignment of edge ether. Overall, the structure of GO upon annealing exhibits interesting, and in some cases unexpected features, which could have a crucial role and applicability to various systems such as vibration-powered energy scavenging, night vision tracking systems and opto-electronics.
*The authors acknowledge funding from the SWAN/NRI program and Texas Instruments.