Comparative Study of Graphite Exfoliation Techniques Using Nafion as a Surfactant
Abstract
1. Introduction
2. Materials and Methods
2.1. Materials
- -
- spectral graphite rods of grade EC-22 (length 19.9 cm, diameter 0.6 cm); density 1.65 g/cm3, porosity 25%, electrical resistivity ≤ 20 µOhm [37];
- -
- graphite foil made of thermally expanded graphite from Graflex®(Graflex, Podolsk, Russia), density ≤ 0.05 g/cm3;
2.2. Methods
2.2.1. UV-Vis
2.2.2. DTA
2.2.3. XRD
2.2.4. DLS
2.2.5. XPS
2.2.6. TEM and Electron Diffraction
2.3. Calculations and Data Processing
2.4. Technologies of Few-Layer Graphene
2.4.1. Ultrasound-Assisted Liquid-Phase Exfoliation (High-Power Ultrasound)
- -
- number of graphene layers;
- -
- particle size;
- -
- monodispersity;
- -
- stability of the dispersion;
- -
- overall process efficiency, including product yield and exfoliation duration.
2.4.2. Electrochemical Exfoliation Followed by Liquid-Phase Exfoliation Using Mild US Treatment
3. Results
3.1. UV-Vis Spectroscopy and Sedimentation Curves
3.2. TEM, ED, and XRD
3.3. DLS
3.4. DTA
3.5. XPS
4. Discussion and Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
XRD | X-ray diffraction |
TGA | thermogravimetric analysis |
ED | electron diffraction |
DLS | dynamic light scattering |
EDX | energy-dispersive X-ray spectroscopy |
XPS | X-ray photoelectron spectroscopy |
PEM | proton exchange membrane |
PEM WE | proton exchange membrane water electrolyzer |
MEAs | membrane electrode assemblies |
PTFE | polytetrafluoroethylene |
PEMFC | proton exchange membrane fuel cells |
rGO | reduced graphene oxide |
GO | graphene oxide |
TEM | transmission electron microscopy |
AFM | atomic force microscopy |
SEM | scanning electron microscopy |
US | ultrasound |
CV | current-voltage |
TG | thermogravimetric |
DT | differential thermal |
CSR | coherent scattering region |
EE | electrochemical exfoliation |
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Sample | Precursor | С (Surfactant), mg/L | Sonication Time, min |
---|---|---|---|
Graphite US 0 mg/L | Spectral graphite | 0 | 13 |
Graphite US 50 mg/L | Spectral graphite | 50 | 13 |
Graphite US 150 mg/L | Spectral graphite | 150 | 13 |
Graphite US 300 mg/L | Spectral graphite | 300 | 13 |
Graphite US 0 min | Spectral graphite | 150 | 0 |
Graphite US 13 min | Spectral graphite | 150 | 13 |
Graphite US 25 min | Spectral graphite | 150 | 25 |
Graphite US 45 min | Spectral graphite | 150 | 45 |
Graflex US 13 min | Graflex | 150 | 13 |
Sample | A550 | Amax (270) | N |
---|---|---|---|
Graphite US 0 mg/L | 1.034 | 1.116 | >11 |
Graphite US 150 mg/L | 0.622 | 0.710 | >11 |
Graphite US 300 mg/L | 0.538 | 0.597 | >11 |
Graphite US 13 min | 0.724 | 0.804 | >11 |
Graphite US 25 min | 0.943 | 1.068 | >11 |
Graphite US 45 min | 1.706 | 2.023 | 10 |
Graflex US 13 min | 1.690 | 2.055 | 10 |
Graphite US 13 min (replicate) | 1.077 | 1.192 | >11 |
Sample | Sonication Time, min | τ1/2, s | A54000/A0 |
---|---|---|---|
Graphite US 0 min | 0 | 1390 | 0.13 |
Graphite US 13 min | 13 | 6900 | 0.68 |
Graphite US 25 min | 25 | 10,700 | 0.73 |
Graphite US 45 min | 45 | 7700 | 0.76 |
Sample | Composition | С (Surfactant), mg/L | Product Yield | |
---|---|---|---|---|
Carbon Material | Surfactant | |||
Graphite US | Spectral graphite | Nafion | 100 | 0.83 |
Graflex US | Graflex | Nafion | 100 | (1.28) associated with partial exfoliation of the auxiliary electrode |
Graphite US w/o surfactant | Spectral graphite | - | 0 | 0.82 |
Sample | Composition | Mode | Product Yield | Charge | Specific Charge, C/g | |
---|---|---|---|---|---|---|
Carbon Material | Nafion, mg/L | |||||
EE-1 | Spectral graphite | 100 | pulse +3 V, −1.5 V, 30 s | 0.78 | +3 V: 9010 C −1.5 V: 3310 C | 24,641 |
EE-2 | Spectral graphite | 100 | potentiostatic +3 V | 0.97 | +3 V: 8493 C | 11,634 |
EE-3 | Spectral graphite | 0 | pulse +3 V, −1.5 V, 30 s | 0.53 | +3 V: 13,285 C −1.5 V: 4953 C | 45,644 |
EE-4 | Graflex | 100 | pulse +3 V, −1.5 V, 30 s | 0.35 | +3 V: 27,887 C −1.5 V: 13,465 C | 143,340 |
Sample | Composition, %wt | С (Nafion), mg/L | N (UV-Vis) | |
---|---|---|---|---|
Carbon Material | Surfactant (Nafion) | |||
Graphite EE | 80 (EE-1) | 20 | 2000 | 7 |
Graflex EE | 80 (EE-4) | 9 |
Sample | A550 | Amax (270) | N |
---|---|---|---|
Graphite US | 0.910 | 1.066 | 10 |
Graflex US | 1.337 | 1.477 | >11 |
Graphite US w/o surfactant | 0.459 | 0.483 | >11 |
Graphite EE | 1.505 | 2.289 | 8 |
Graphite EE (replicate) | 0.821 | 1.348 | 7 |
Graflex EE | 1.341 | 1.894 | 9 |
Sample | C Carbon, g/L | τ1/2, s | A54000/A0 |
---|---|---|---|
EE-1 | 15 | 534 | 0.0302 |
EE-2 | 15 | 72 | 0.0675 |
EE-3 | 15 | 504 | 0.0253 |
EE-4 | 15 | 170 | - |
Graphite EE | 0.24 | >54,000 | 0.905 |
Graphite US | 3.8 | >54,000 | 0.720 |
Graflex US | 0.38 | 46,200 | 0.488 |
Graphite US w/o surfactant | 15 | 19 | 0.0131 |
Graflex EE | 0.24 | >54,000 | 0.949 |
Sample | Position (hkl), 2θ | Average CSR Size (hkl), Å | FWHM (hkl), 2θ | d (002), Å | Number of Layers | G | AS | |||
---|---|---|---|---|---|---|---|---|---|---|
(002) | (100) | (002) | (100) | (002) | (100) | N = Lc/d(002) | A = La/Lc | |||
Graphite pristine | 26.504 | 42.393 | 308.480 | 270.100 | 0.276 | 0.329 | 3.360 | 91.8 | 0.927 | 0.876 |
EE-1 | 26.474 | 42.439 | 169.700 | 264.190 | 0.487 | 0.342 | 3.364 | 50.4 | 0.883 | 1.557 |
EE-1 (replicate) | 26.487 | 42.462 | 168.300 | 249.000 | 0.510 | 0.358 | 3.363 | 50.1 | 0.900 | 1.480 |
Graphite US | 26.463 | 42.405 | 378.913 | 259.140 | 0.225 | 0.343 | 3.365 | 112.6 | 0.867 | 0.684 |
Graphite EE | 26.448 | - | 149.711 | 17.733 | 0.570 | 5.040 | 3.367 | 44.5 | 0.845 | 0.118 |
Graflex pristine | 26.500 | - | 220.833 | - | 0.386 | - | 3.361 | 65.7 | 0.921 | - |
Graflex US | 26.471 | 42.486 | 169.922 | 266.130 | 0.502 | 0.333 | 3.364 | 50.5 | 0.879 | 1.566 |
Graflex EE | 26.468 | - | 103.344 | - | 0.825 | - | 3.365 | 30.7 | 0.874 | - |
Sample | Max, nm | Particle Fraction, % | Size Range, nm | FWHM, nm | ζ-Potential, mV |
---|---|---|---|---|---|
Graphite EE (1st peak) | 91 | 13 | 59–1106 | 198 | −35 |
Graphite EE (2nd peak) | |||||
Graphite US | 255 | 17 | 106–712 | 195 | −28.1 |
Graphite US w/o surfactant | 5560 | 18 | 2669–10,000 | 4180 | −5.9 |
Graflex EE (1st peak) | 1281 | 21 | 712–2305 | 755 | - |
Graflex EE (2nd peak) | 7456 | 5 | 4801–10,000 | 3050 | |
Graflex US | 4801 | 34 | 3091–6439 | 1959 | −27.2 |
Sample | Atomic % (XPS Survey Spectrum) | Ratios | ||||
---|---|---|---|---|---|---|
C1s | F1s | O1s | S2p |
C1s/O1s
(Carbon Material) | F1s/S2p | |
Graphite US | 71.40 | 24.19 | 3.90 | 0.51 | 37.48 | 47.43 |
Graflex US | 94.86 | 2.68 | 2.32 | 0.15 | 45.31 | 17.87 |
Graphite EE | 61.17 | 31.00 | 7.16 | 0.67 | 11.22 | 46.27 |
Graflex EE | 75.27 | 17.03 | 7.27 | 0.43 | 11.97 | 39.60 |
Nafion | 28.14 | 64.25 | 6.05 | 1.55 | - | 41.45 |
Sample | C=C | C–C | –CF2 | –CF3 | O–C–F | C–O–C | O–C=O | sp2/sp3 | C/O |
---|---|---|---|---|---|---|---|---|---|
Graphite US | 59.9 | 10.3 | 13.4 | 2.0 | 2.7 | 8.4 | 3.4 | 5.8 | 13.38 |
Graflex US | 69.0 | 11.7 | 4.6 | 1.3 | 3.3 | 5.8 | 4.4 | 5.9 | 35.56 |
Graphite EE | 54.5 | 7.9 | 15.5 | 4.0 | 4.6 | 9.1 | 4.5 | 6.9 | 5.50 |
Graflex EE | 63.5 | 9.8 | 9.5 | 2.0 | 2.9 | 7.3 | 5.0 | 6.5 | 7.82 |
Nafion | 0 | 12.8 | 67.7 | 14.3 | 0 | 5.2 | 0 | - | - |
Sample | Graphite US | Graflex US | Graphite EE | Graflex EE |
---|---|---|---|---|
Number of graphene layers (XRD data) | ~100 | ~50 | ~45 | ~30 |
Number of graphene layers (TEM data) | 100 | 1–2 | 15 | 1–2 |
Lateral size (DLS and TEM data), nm | 100–300 | >1000 | 100–300 | >1000 |
C/O (C1s XPS spectra) | 13.38 | 35.56 | 5.50 | 7.82 |
Product yield, % | 98 | 98 | 76 | 33 |
Time of synthesis, min | 45 | 45 | 500 + 1800 | 528 + 1800 |
Energy input, kWh | 0.75 | 0.75 | 0.012 + 3.9 | 0.034 + 3.9 |
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Krasnova, A.O.; Glebova, N.V.; Nechitailov, A.A.; Kastsova, A.G.; Pelageikina, A.O.; Kirilenko, D.A.; Shvidchenko, A.V.; Shestakov, M.S.; Koroleva, A.V.; Khrapova, E.K. Comparative Study of Graphite Exfoliation Techniques Using Nafion as a Surfactant. C 2025, 11, 76. https://doi.org/10.3390/c11040076
Krasnova AO, Glebova NV, Nechitailov AA, Kastsova AG, Pelageikina AO, Kirilenko DA, Shvidchenko AV, Shestakov MS, Koroleva AV, Khrapova EK. Comparative Study of Graphite Exfoliation Techniques Using Nafion as a Surfactant. C. 2025; 11(4):76. https://doi.org/10.3390/c11040076
Chicago/Turabian StyleKrasnova, Anna O., Nadezhda V. Glebova, Andrey A. Nechitailov, Angelina G. Kastsova, Anna O. Pelageikina, Demid A. Kirilenko, Alexander V. Shvidchenko, Mikhail S. Shestakov, Aleksandra V. Koroleva, and Ekaterina K. Khrapova. 2025. "Comparative Study of Graphite Exfoliation Techniques Using Nafion as a Surfactant" C 11, no. 4: 76. https://doi.org/10.3390/c11040076
APA StyleKrasnova, A. O., Glebova, N. V., Nechitailov, A. A., Kastsova, A. G., Pelageikina, A. O., Kirilenko, D. A., Shvidchenko, A. V., Shestakov, M. S., Koroleva, A. V., & Khrapova, E. K. (2025). Comparative Study of Graphite Exfoliation Techniques Using Nafion as a Surfactant. C, 11(4), 76. https://doi.org/10.3390/c11040076