Functional Properties of Mechanically Exfoliated Graphene

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Journal Title
Journal ISSN
Volume Title
School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2019-12-12
Date
2019
Major/Subject
Mcode
Degree programme
Language
en
Pages
95 + app. 87
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 228/2019
Abstract
Graphene is an exciting 2-dimensional material with a wide range of superior properties, such as excellent thermal and electrical conductivity, high transparency, surface area and mechanical strength. However, a wider scale application still depends on finding viable large-scale production methods of high quality graphene. This thesis demonstrates a feasible method for fabrication of graphene with scalability potential. High concentration and quality of mechanically exfoliated graphene (in short, pristine graphene), was achieved at short processing time using shear exfoliation. This mechanically exfoliated graphene was further used to fabricate functional nanopapers with a wide range of properties, and as electrode materials for supercapacitor application. The properties of pristine graphene were also compared to other types of graphene, namely graphene oxide (GO) and reduced graphene oxide (RGO), in nanocomposite films designed for functional applications formed as graphene-doped microfibrillated cellulose (MFC) nanopapers. The different surface chemistry of these grades of graphene led to the fabrication of composites with a wide range of properties due to their unique interaction with the MFC polymer matrix. For example, pristine graphene led to a high electrical conductivity and thermal stability, while GO and RGO led to enhanced mechanical properties of the nanopapers. The composites can be tailored for a wide range of potential applications, such as flexible electronics, sensors, electrodes etc. Following these foreseen advantages, the nanopapers were further developed for testing in application as electrode materials in supercapacitors. This was realized by converting into carbon hybrids by activation with KOH to introduce properties suitable for good electrochemical performance. MFC was used to stabilize and exfoliate the graphene and as a binder in the electrodes. The electrodes showed excellent electrochemical performance with potential for application in various devices. Furthermore, the performance of the carbon hybrids was compared with willow-derived activated carbon in supercapacitors. The willow-derived activated carbon showed even higher capacitance than the carbon hybrids. However, the carbon hybrids showed much better cycling stability, 99% capacitance retention after 5 000 cycles versus 94% for willow derived activated carbons. The work summarized in this thesis, in conclusion, contributes to the development of graphene for larger scale commercial application, identifying potential routes for fabrication of high performance functional carbon materials based on alternative renewable and sustainable materials to replace the currently potentially toxic, and hazardous chemical additives.
Description
Supervising professor
Maloney, Thaddeus, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Thesis advisor
Maloney, Thaddeus, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Keywords
graphene, supercapacitor, electrodes, graphite, graphene oxide, nanocellulose, microfibrillated cellulose, energy storage devices
Other note
Parts
  • [Publication 1]: Phiri, J., Gane, P., Maloney, T.C. High-concentration shear-exfoliated colloidal dispersion of surfactant–polymer-stabilized few-layer graphene sheets. Journal of Materials Science, 2017, 52(13), 8321-8337.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201905062697
    DOI: 10.1007/s10853-017-1049-y View at publisher
  • [Publication 2]: Phiri, J., Johansson, L.S., Gane, P., Maloney, T.C. Co-exfoliation and fabrication of graphene based microfibrillated cellulose composites–mechanical and thermal stability and functional conductive properties. Nanoscale, 2018, 10(20), 9569-9582.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201905062784
    DOI: 10.1039/C8NR02052C View at publisher
  • [Publication 3]: Phiri, J., Johansson, L.S., Gane, P., Maloney, T. A comparative study of mechanical, thermal and electrical properties of graphene-, graphene oxideand reduced graphene oxide-doped microfibrillated cellulose nanocomposites. Composites Part B: Engineering, 2018, 147, 104-113.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201905062745
    DOI: 10.1016/j.compositesb.2018.04.018 View at publisher
  • [Publication 4]: Phiri, J., Gane, P., Maloney, T.C. Multidimensional Co‐Exfoliated Activated Graphene‐Based Carbon Composite for Supercapacitor Electrode. Energy Technology. 2019, 7: 1900578.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201909205307
    DOI: 10.1002/ente.201900578 View at publisher
  • [Publication 5]: Phiri, J., Dou, J., Vuorinen, T., Gane, P.A., Maloney, T.C. Highly Porous Willow Wood-Derived Activated Carbon for High-Performance Supercapacitor Electrodes. ACS Omega, 2019, 4, 19, 18108-18117.
    DOI: 10.1021/acsomega.9b01977 View at publisher
Citation