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Ion percolation through annealed, supported graphene oxide films: Role of nanochannels and voids
Vasumathy Ravishankar, ,
Published in American Institute of Physics Inc.
2019
Volume: 125
   
Issue: 14
Abstract
Graphene oxide (GO), an ionic and molecular sieve, is an important material for wide-spectrum filtration, since its properties can be tuned by controlling the structure and dimensions of nanochannels between GO nanosheets. In the literature, mechanisms of ion percolation have been proposed assuming GO to be a uniform structure of vertically stacked graphene sheets decorated with functional groups, termed as lamellae. However, in practice, GO is known to have a hierarchical microstructure. In the present work, supported GO films annealed at different temperatures have been studied with the aim of discerning the relative contributions of nanochannels and voids, gaps between the lamellae, using electro-impedance spectroscopy, and the results were fitted to equivalent circuits. Monotonous decrease in the charge transfer resistance Rct and an increase in the percolation resistance RP were observed for GO films annealed up to 160 °C. Increase in RP, taken in perspective with a gradual loss of ordering in nanosheets as observed from X-ray diffraction spectra, enables the conclusion that nanochannels are the dominant pathways of percolation. This was further confirmed by the response of GO films annealed at 180 °C and 200 °C, where a strong dynamic is observed. For these annealed GO films, charge transfer happens both in the conducting films and at the fluorine-doped tin oxide interface. The two processes of ion percolation and charge transfer are, however, interdependent, and are not separated in the impedance response. © 2019 Author(s).
About the journal
JournalData powered by TypesetJournal of Applied Physics
PublisherData powered by TypesetAmerican Institute of Physics Inc.
ISSN00218979
Open AccessNo
Concepts (20)
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    Annealing
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    Charge transfer
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    Conductive films
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    Equivalent circuits
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    Graphene
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    Ions
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    Molecular sieves
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    Nanocomposites
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    Nanosheets
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    Solvents
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    TIN OXIDES
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    Charge transfer resistance
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    ELECTRO IMPEDANCE SPECTROSCOPIES
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    FLUORINE DOPED TIN OXIDE
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    HIERARCHICAL MICROSTRUCTURES
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    Impedance response
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    PERCOLATION RESISTANCE
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    Relative contribution
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    X-ray diffraction spectrum
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    Oxide films