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

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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.


(a) The CV curves at different scan rates, (b) the specific capacitance versus scan rate, (c) galvanostatic charge/discharge curves at the different current densities of T-GR, and (d) Capacitance retention ratio as a function of the potential sweep rates for T-GR supercapacitors up to 5,000 cycles. Inset: A configuration of a test cell for electrochemical measurement.
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f6: (a) The CV curves at different scan rates, (b) the specific capacitance versus scan rate, (c) galvanostatic charge/discharge curves at the different current densities of T-GR, and (d) Capacitance retention ratio as a function of the potential sweep rates for T-GR supercapacitors up to 5,000 cycles. Inset: A configuration of a test cell for electrochemical measurement.

Mentions: Figure 6 shows the electrochemical properties of the T-GR that were obtained with the organic and aqueous systems. After synthesizing highly-porous, single-layered graphene, the performance of the T-GR supercapacitor was investigated by a symmetrical, two-electrode system in an organic electrolyte. Figure 6a shows the CV of the highly-porous, single-layered graphene supercapacitor in 6-M KOH as an aqueous system at different scan rates. It can be seen that all CV curves at the different scan rates presented a rectangular shape, which is indicative of excellent charge propagation at the electrode surface as well as following the electric double layer capacitive properties of T-GR. The specific capacitance of T-GR was obtained by calculating the integrated area of CV, as observed in the Supplementary information. The specific capacitance of T-GR for different scanning rates is shown in Fig. 6b. It is seen that the specific capacitance decreased as the scanning rate increased. When the scanning rate increased to its maximum value of 100 mV/s, the capacitance still presented a fairly high extent of 264 F/g, almost 75% of the maximum capacitance of 354 F/g at the scanning rate of 5 mV/s. Compared with previous studies of the graphene family summarized in Table S1 23273644454647484950, the T-GR with a capacitance of 354.1 Fg−1 at 5 mVs−1, exhibits excellent performance as a supercapacitor.


Mass production of highly-porous graphene for high-performance supercapacitors
(a) The CV curves at different scan rates, (b) the specific capacitance versus scan rate, (c) galvanostatic charge/discharge curves at the different current densities of T-GR, and (d) Capacitance retention ratio as a function of the potential sweep rates for T-GR supercapacitors up to 5,000 cycles. Inset: A configuration of a test cell for electrochemical measurement.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: (a) The CV curves at different scan rates, (b) the specific capacitance versus scan rate, (c) galvanostatic charge/discharge curves at the different current densities of T-GR, and (d) Capacitance retention ratio as a function of the potential sweep rates for T-GR supercapacitors up to 5,000 cycles. Inset: A configuration of a test cell for electrochemical measurement.
Mentions: Figure 6 shows the electrochemical properties of the T-GR that were obtained with the organic and aqueous systems. After synthesizing highly-porous, single-layered graphene, the performance of the T-GR supercapacitor was investigated by a symmetrical, two-electrode system in an organic electrolyte. Figure 6a shows the CV of the highly-porous, single-layered graphene supercapacitor in 6-M KOH as an aqueous system at different scan rates. It can be seen that all CV curves at the different scan rates presented a rectangular shape, which is indicative of excellent charge propagation at the electrode surface as well as following the electric double layer capacitive properties of T-GR. The specific capacitance of T-GR was obtained by calculating the integrated area of CV, as observed in the Supplementary information. The specific capacitance of T-GR for different scanning rates is shown in Fig. 6b. It is seen that the specific capacitance decreased as the scanning rate increased. When the scanning rate increased to its maximum value of 100 mV/s, the capacitance still presented a fairly high extent of 264 F/g, almost 75% of the maximum capacitance of 354 F/g at the scanning rate of 5 mV/s. Compared with previous studies of the graphene family summarized in Table S1 23273644454647484950, the T-GR with a capacitance of 354.1 Fg−1 at 5 mVs−1, exhibits excellent performance as a supercapacitor.

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.