The Exfoliation of Graphene in Liquids by Electrochemical, Chemical, and Sonication‐Assisted Techniques: A Nanoscale Study

Xia, Zhenyuan; Pezzini, Sergio; Treossi, Emanuele; Giambastiani, Giuliano; Corticelli, Franco; Morandi, Vittorio; Zanelli, Alberto; Bellani, V.; Palermo, Vincenzo

doi:10.1002/adfm.201203686

Cited by 152 publications

(175 citation statements)

References 31 publications

(41 reference statements)

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“…[56][57][58] The penetration of oxidizing agents might again cause augmented oxidation of the graphite resulting in an increasing amount of ketone groups accompanied by hydroxyl groups. [58][59][60] Recently, Deheryan et al 61 reported that the magnitude of the capacitive currents can be correlated with θ for carbon nanosheets. Thus it is expected that C dl measured for the BPPs is directly coupled to the specific surface area of graphite, which was in contact with the sulfuric acid during CV measurement.…”

Section: Resultsmentioning

confidence: 99%

Chemical Stability of Graphite-Polypropylene Bipolar Plates for the Vanadium Redox Flow Battery at Resting State

Satola

Kirchner

Komsiyska

et al. 2016

J. Electrochem. Soc.

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Current collectors called bipolar plates (BPP) are important elements within the conversion unit of the vanadium redox flow battery (VRFB). They are in direct contact with acidic electrolytes, containing vanadium species in different oxidation states. The influence of the state of charge (SOC) on the calendar aging of BPPs was examined. Graphite-polypropylene BPPs were immersed in positive and negative vanadium electrolytes at 0%, 20%, 80% and 100% SOC for 30, 90 and 190 days. H 2 gas evolution was observed as side reaction on the surface of the BPPs in the negative electrolyte. After electroless aging, scanning electron (SEM) and confocal microscopy measurements showed no significant changes in the surface morphology. The electrical conductivities of the BPPs were not affected significantly. However, contact angle (θ) measurements revealed that the positive electrolyte influenced the wettability of the BPPs. X-ray photoelectron (XP) spectroscopy showed progressing oxidation of the BPP surfaces in the positive electrolyte and adsorption or entrapment of vanadium ions in the pores at high SOC. Cyclic voltammograms (CV) provided evidence that the graphite was oxidized combined with an increase in effective surface area. ATR-FTIR measurements showed slight oxidation of pure polypropylene granulate in the positive electrolyte with 100% SOC. The increasing energy power supply from intermittent renewable energy sources requires a rapid introduction of efficient energy storages. One promising technology is the vanadium redox flow battery (VRFB), as it enables to scale the power and the storage capacity independently according to specific requirements.1,2 In addition the VRFB is characterized by a fast response time and long electrolyte cycle life.3 Each reaction unit in a VRFB stack is composed of two half-cells separated by a membrane consisting of an electrode in contact with a current collector called bipolar plate (BPP).2 In a battery stack the BPPs are "non-active" components that conduct current from one cell to the other. They physically separate adjacent cells from each other while staying in contact with acidic half-cell electrolytes containing vanadium species in different oxidation states on each side. 4 For brevity we call the V 2+ /V 3+ solution "negative electrolyte" and the VO 2+ /VO 2 + solution "positive electrolyte". While vanadium redox reactions mainly occur on the surfaces of the porous electrodes, they could also occur unintentionally on the surfaces of the BPPs. [5][6][7] Therefore, a good BPP should be characterized by a high chemical and mechanical stability, high electrical conductivity and impermeability to preclude leakage. 8 Metallic BPPs are usually not used in VRFB as they corrode in acidic environments and would need a protective layer.5,9,10 Therefore, graphite based BPPs are commonly used as they possess a good electrical conductivity and a better chemical stability. 4 However, pure graphite plates are not favored as BPPs due to their high weight and cost as well as low mechanical stre...

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Section: Resultsmentioning

confidence: 99%

Chemical Stability of Graphite-Polypropylene Bipolar Plates for the Vanadium Redox Flow Battery at Resting State

Satola

Kirchner

Komsiyska

et al. 2016

J. Electrochem. Soc.

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“…The effi cient intercalation as well as gas eruption promote the separation of graphene sheets from neighboring graphene layers. [ 23 ] Moreover, water is crucial for the overall exfoliation process, as it not only serves as a solvent to decrease the viscosity of the solution, but also produces reactive oxygen-containing species from anodic oxidation, which in turn corrode the graphite anode at grain boundaries or edges, facilitating SO 4 2− intercalation. [ 24 ] However, in acidic electrolytes, the ion intercalation is so fast that it occurs simultaneously with exfoliation at all graphite edges, in contrast to the ideal model, where graphene layers peel off layer by layer individually.…”

Section: Research Newsmentioning

confidence: 99%

“…By monitoring the structural deformation at the graphite interface, Palermo et al have proven that effi cient intercalation and bubble formation inside graphite interlayers are important factors governing fast and complete exfoliation. [ 23 ] In practice, exfoliation begins at any part of graphite and these stages do not occur in order, which is the main reason for the wide distribution of graphene layers. There seems to be a trade-off between the effi ciency of exfoliation and the preservation of graphene quality.…”

Section: Understanding Of the Exfoliation Mechanismmentioning

confidence: 99%

New‐Generation Graphene from Electrochemical Approaches: Production and Applications

et al. 2016

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Extensive research suggests a bright future for the graphene market. However, for a long time there has been a huge gap between laboratory-scale research and commercial application due to the challenging task of reproducible bulk production of high-quality graphene at low cost. Electrochemical exfoliation of graphite has emerged as a promising wet chemical method with advantages such as upscalability, solution processability and eco-friendliness. Recent progress in the electrochemical exfoliation of graphite and prospects for the application of exfoliated graphene, mainly in the fields of composites, electronics, energy storage and conversion are discussed.

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“…Several liquids were used to create stable dispersions of graphene such as surfactants in aqueous media, ionic liquids and organic solvents. [10][11][12][13][14][15] The organic solvent ortho-dichlorobenzene (o-DCB), being aromatic, is able to interact with graphene via π -π stacking. o-DCB has a surface tension of 36.6 mJ/m 2 , which is very close to the proposed range (40-50 mJ/m 2 ).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of few layer graphene by direct exfoliation of graphite and a Raman spectroscopic study

Gayathri

Prakash

Kottaisamy³

et al. 2014

AIP Advances

186

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The exfoliation of graphene from pristine graphite in a liquid phase was achieved successfully via sonication followed by centrifugation method. Ultraviolet–visible (UV–vis) spectra of the obtained graphene dispersions at different exfoliation time indicated that the concentration of graphene dispersion increased markedly with increasing exfoliation time. The sheet-like morphology of the exfoliated graphene was revealed by Scanning Electron Microscopy (SEM) image. Further, the morphological change in different exfoliation time was investigated by Atomic Force Microscopy (AFM). A complete structural and defect characterization was probed using micro-Raman spectroscopic technique. The shape and position of the 2D band of Raman spectra revealed the formation of bilayer to few layer graphene. Also, Raman mapping confirmed the presence of uniformly distributed bilayer graphene sheets on the substrate.

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The Exfoliation of Graphene in Liquids by Electrochemical, Chemical, and Sonication‐Assisted Techniques: A Nanoscale Study

Cited by 152 publications

References 31 publications

Chemical Stability of Graphite-Polypropylene Bipolar Plates for the Vanadium Redox Flow Battery at Resting State

Chemical Stability of Graphite-Polypropylene Bipolar Plates for the Vanadium Redox Flow Battery at Resting State

New‐Generation Graphene from Electrochemical Approaches: Production and Applications

Synthesis of few layer graphene by direct exfoliation of graphite and a Raman spectroscopic study

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