Synergistic production of graphene microsheets by simultaneous anodic and cathodic electro-exfoliation of graphitic electrodes in aprotic ionic liquids

Najafabadi, Amin Taheri; Gyenge, Előd L.

doi:10.1016/j.carbon.2014.12.041

Cited by 50 publications

(27 citation statements)

References 55 publications

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“…More to the point, the present results indicate that graphene nanosheets obtained from graphite foil are significantly less oxidized than their HOPG-derived counterparts (see Table 1), even though they are prepared under exactly the same conditions and exhibit the same (high) degree of exfoliation. For instance, the O/C ratio of graphene obtained by 15 min of electrolysis of graphite foil was as low as 0.058, compared with 0.091 for its HOPG-derived equivalent, the former figure being similar to, or even lower than, the values that have been reported for many cathodically exfoliated graphenes [21][22][23][24]64,65]. Another advantage of using graphite foil vs. HOPG lies in its much lower price ($$0.1 per gram compared with $$100 per gram for HOPG).…”

Section: Processing and Characteristics Of Graphene Materials Derivedsupporting

confidence: 48%

High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

Munuera

Paredes

Villar–Rodil

et al. 2015

Carbon

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a b s t r a c tAnodic exfoliation of graphite has emerged as an attractive method to access graphene nanosheets in large quantities, but oxidation reactions associated to this process compromise the structural quality of the resulting materials. Here, we demonstrate that the type of starting graphite material impacts the oxygen and defect content of anodically exfoliated graphenes obtained thereof. We investigated highly oriented pyrolytic graphite (HOPG) as well as graphite foil, flakes and powder as electrode in the anodic process. Importantly, materials with low levels of oxidation and disorder (similar to those typically achieved with cathodic exfoliation approaches) could be attained through proper choice of the graphite electrode. Specifically, using graphite foil afforded nanosheets of higher quality than that of HOPG-derived nanosheets. This discrepancy was interpreted to arise from the structural peculiarities of the former, where the presence of folds, voids and wrinkles would make its exfoliation process to be less reliant on oxidation reactions. Furthermore, cell viability tests carried out with murine fibroblasts on thin graphene films suggested that the anodically exfoliated graphenes investigated here (possessing low or high oxidation levels) are highly biocompatible. Overall, control upon the extent of oxidation and disorder should expand the scope of anodically exfoliated graphenes in prospective applications.

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Section: Processing and Characteristics Of Graphene Materials Derivedsupporting

confidence: 48%

High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

Munuera

Paredes

Villar–Rodil

et al. 2015

Carbon

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“…To the best of our knowledge, the simultaneous production in aqueous medium of carbon‐based nanomaterials, at both cathode and anode of graphite, is reported here for the first time. Although, the simultaneous electrochemical production of graphene flakes and graphene sheets in both anodic and cathodic compartments has been previously reported, it used protic ionic liquids, wherein the intercalation of cations and anions at the cathode and anode of graphite, respectively, was responsible for the electroexfoliation process …”

Section: Resultsmentioning

confidence: 99%

“…Although, the simultaneous electrochemical production of graphene flakes and graphene sheets in both anodic and cathodic compartments has been previously reported, it used protic ionic liquids, wherein the intercalation of cations and anions at the cathode and anode of graphite, respectively, was responsible for the electroexfoliation process. [15,16] The HRTEM images of the synthesized material were poorly resolved due to the low contrast between the amorphous carbon-based material and the formvar grid (Figure 2 SI). Instead, those obtained with a TEM equipment assembled with a 100 keV beam (Figure 1b and 1g) enabled a clearer contrast, showing unequivocally that a carbon-based material is on the grid surface.…”

Section: Resultsmentioning

confidence: 99%

One‐Step Cathodic and Anodic Synthesis of Hydrophilic Carbon Nanomaterials

et al. 2017

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It was demonstrated that the galvanostatic polarization of graphite electrodes in a cell with two separated compartments generates simultaneously and straightforwardly, without further separation and functionalization, two distinct sets of hydrophilic carbon nanomaterials [electrogenerated hydrophilic carbon (EHC)], in the anodic and cathodic compartments, respectively. The synthesized products comprise an amorphous carbonaceous material with aromatic sp2 carbon clusters, differing mainly in their oxidation degree. Surprisingly, it was found that nitrogen is incorporated in the carbon‐based material during the electrolysis, which is provided by the N2 gas present in the air and/or aqueous medium. This phenomenon is explained on the basis that very reactive carbonaceous species are formed during the electrodes polarization, owing to an anomalous high electric field generated along the galvanostatic polarization. In addition, it was also evidenced that ECH materials display a negative charge, counterbalanced by sodium ions and unique optical properties, exhibiting deep ultraviolet emission (ca. 4.1 eV), as well as blue luminescence. It is foreseen that these carbon materials will have important repercussions in optoelectronics devices, energy technology (supercapacitors, batteries, and fuel cells), and biomedicine.

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“…Such an approach boasts a number of assets that are not always present in other potentially scalable methods of graphene production, such as simplicity of operation, versatility (e.g., in terms of electrolyte choice), alacrity (short processing times) and cost-effectiveness. The electrochemical process of graphite delamination to give graphene nanosheets can be carried out under either cathodic or anodic conditions [3,4], or by a combination of both [6,7]. Cathodic exfoliation typically makes use of lithium or alkylammonium salts in organic solvents as the electrolytic system, yielding graphene materials of a high structural quality and limited oxidation (O/C atomic ratios of ~0.03-0.08) [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

High quality, low-oxidized graphene via anodic exfoliation with table salt as an efficient oxidation-preventing co-electrolyte for water/oil remediation and capacitive energy storage applications

Munuera

Paredes

Villar–Rodil

et al. 2018

Applied Materials Today

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The production of graphene through anodic exfoliation of graphite in water is regarded as a competitive approach in the efforts to scale-up the manufacturing of this two-dimensional material for different practical uses. However, issues related to oxidative attack of the nanosheets inherent to this delamination process have traditionally precluded the attainment of high quality materials, with the use of proper electrolyte additives as oxidation-preventing agents being proposed as a possible way out. Here we demonstrate that sodium chloride (table salt) can be used as a highly efficient additive (co-electrolyte) of common sulfate-based electrolytes, yielding anodically exfoliated graphene with minimal oxidation (O/C ratio ~0.02-0.03) and thus a high structural quality. As an oxidation-preventing co-electrolyte, sodium chloride clearly outperformed other tested additives, including sodium borohydride, sulfite, citrate, bromide and iodide, ascorbic acid or ethanol, as well as other recently reported chemical species of a more complex nature and/or less readily available. The apparently contradicting ability of the chloride anion to avert oxidation of anodic graphene without negatively interfering with the exfoliation process itself was also discussed and ultimately ascribed to the different chemical reactivity of graphite edges and basal planes. The as-prepared, low-oxidized graphene exhibited a notable adsorption capacity towards organic dyes in aqueous solution (e.g., ~450 mg g -1 for methyl orange), a substantial ability to absorb oils and non-polar organic solvents (15-30 g g -1 ), and displayed a good capacitive energy storage behavior (e.g., ~120 F g -1 at 0.1 A g -1 ), all without the need of any post-processing steps that are so common for graphene-based materials. Overall, the demonstration that low-oxidized anodic graphene can be obtained by resorting only to inexpensive and widely available reagents should facilitate the implementation of this methodology in the industrial manufacturing of high quality graphene for several applications.

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Synergistic production of graphene microsheets by simultaneous anodic and cathodic electro-exfoliation of graphitic electrodes in aprotic ionic liquids

Cited by 50 publications

References 55 publications

High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

One‐Step Cathodic and Anodic Synthesis of Hydrophilic Carbon Nanomaterials

High quality, low-oxidized graphene via anodic exfoliation with table salt as an efficient oxidation-preventing co-electrolyte for water/oil remediation and capacitive energy storage applications

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