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Mass production of highly-porous graphene for high-performance supercapacitors

View Article: PubMed Central - PubMed

ABSTRACT

This study reports on a facile and economical method for the scalable synthesis of few-layered graphene sheets by the microwave-assisted functionalization. Herein, single-layered and few-layered graphene sheets were produced by dispersion and exfoliation of functionalized graphite in ethylene glycol. Thermal treatment was used to prepare pure graphene without functional groups, and the pure graphene was labeled as thermally-treated graphene (T-GR). The morphological and statistical studies about the distribution of the number of layers showed that more than 90% of the flakes of T-GR had less than two layers and about 84% of T-GR were single-layered. The microwave-assisted exfoliation approach presents us with a possibility for a mass production of graphene at low cost and great potentials in energy storage applications of graphene-based materials. Owing to unique surface chemistry, the T-GR demonstrates an excellent energy storage performance, and the electrochemical capacitance is much higher than that of the other carbon-based nanostructures. The nanoscopic porous morphology of the T-GR-based electrodes made a significant contribution in increasing the BET surface as well as the specific capacitance of graphene. T-GR, with a capacitance of 354.1 Fg−1 at 5 mVs−1 and 264 Fg−1 at 100 mVs−1, exhibits excellent performance as a supercapacitor.

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(a) XPS survey spectra of CE-GR and T-GR. High-resolution C 1 s spectra of (b) pristine graphite, (c) CE-GR and (d) T-GR.
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f2: (a) XPS survey spectra of CE-GR and T-GR. High-resolution C 1 s spectra of (b) pristine graphite, (c) CE-GR and (d) T-GR.

Mentions: The natures of pristine graphite, CE-GR, and T-GR were studied by X-ray photoelectron spectroscopy (XPS), as illustrated in Fig. 2a. It can be seen that C 1 s and O 1 s peaks appeared at ~284.5 eV and 531.8 eV, respectively. Based on these results, pristine graphite presents a very small amount of oxygen. Upon functionalization, the intensity of the O 1 s peak increased considerably. It is obvious that PEG functionalities may explain the higher content of oxygen in the CE-GR sample. The amount of oxygen in T-GR decreased after thermal treatment in nitrogen as compared with the CE-GR sample, and, interestingly, it was a bit lower than the amount of oxygen in pristine graphite. The decrease in the O component that was obtained after thermal treatment was associated with the loss of the functional groups between the graphene layers, which was in agreement with the FTIR, TGA, DTG, and Raman results. To investigate the nature of the functional groups, further study was conducted using high-resolution C 1 s scans. Figure 2b–d present the deconvoluted C1s XPS spectra of pristine graphite, CE-GR, and T-GR.


Mass production of highly-porous graphene for high-performance supercapacitors
(a) XPS survey spectra of CE-GR and T-GR. High-resolution C 1 s spectra of (b) pristine graphite, (c) CE-GR and (d) T-GR.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015014&req=5

f2: (a) XPS survey spectra of CE-GR and T-GR. High-resolution C 1 s spectra of (b) pristine graphite, (c) CE-GR and (d) T-GR.
Mentions: The natures of pristine graphite, CE-GR, and T-GR were studied by X-ray photoelectron spectroscopy (XPS), as illustrated in Fig. 2a. It can be seen that C 1 s and O 1 s peaks appeared at ~284.5 eV and 531.8 eV, respectively. Based on these results, pristine graphite presents a very small amount of oxygen. Upon functionalization, the intensity of the O 1 s peak increased considerably. It is obvious that PEG functionalities may explain the higher content of oxygen in the CE-GR sample. The amount of oxygen in T-GR decreased after thermal treatment in nitrogen as compared with the CE-GR sample, and, interestingly, it was a bit lower than the amount of oxygen in pristine graphite. The decrease in the O component that was obtained after thermal treatment was associated with the loss of the functional groups between the graphene layers, which was in agreement with the FTIR, TGA, DTG, and Raman results. To investigate the nature of the functional groups, further study was conducted using high-resolution C 1 s scans. Figure 2b–d present the deconvoluted C1s XPS spectra of pristine graphite, CE-GR, and T-GR.

View Article: PubMed Central - PubMed

ABSTRACT

This study reports on a facile and economical method for the scalable synthesis of few-layered graphene sheets by the microwave-assisted functionalization. Herein, single-layered and few-layered graphene sheets were produced by dispersion and exfoliation of functionalized graphite in ethylene glycol. Thermal treatment was used to prepare pure graphene without functional groups, and the pure graphene was labeled as thermally-treated graphene (T-GR). The morphological and statistical studies about the distribution of the number of layers showed that more than 90% of the flakes of T-GR had less than two layers and about 84% of T-GR were single-layered. The microwave-assisted exfoliation approach presents us with a possibility for a mass production of graphene at low cost and great potentials in energy storage applications of graphene-based materials. Owing to unique surface chemistry, the T-GR demonstrates an excellent energy storage performance, and the electrochemical capacitance is much higher than that of the other carbon-based nanostructures. The nanoscopic porous morphology of the T-GR-based electrodes made a significant contribution in increasing the BET surface as well as the specific capacitance of graphene. T-GR, with a capacitance of 354.1 Fg−1 at 5 mVs−1 and 264 Fg−1 at 100 mVs−1, exhibits excellent performance as a supercapacitor.

No MeSH data available.