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Fig. 2. XRD pattern for the ACMs from non-irradiated and y-irradiated GMs at different y-radiation dosage.

Figure 2 XRD pattern for the ACMs from non-irradiated and y-irradiated GMs at different y-radiation dosage.

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Fig. 1. FTIR spectra for non-irradiated and y-irradiated GMs at different y-radiation doses. The FTIR spectra in the range of wavenumbers from 400 to 4000 cm™! for GM and y-irradiated GM samples are shown in Fig. 1. The patterns of prominent peaks or bands in Fig. 1 for non- irradiated GMs are typical for lignocellulosic materials and are similar to those in the FTIR spectra reported for EFB [59,60], dried date pits [61] and jute fibers [62]. Assignments of these bands to their corresponding functional groups were reported in Refs. {63—65] for EFB samples, and in general, the bands involved C—O and C—H bonds in the macromolecules found in the EFB. Some differences between the FTIR spectra of the non-irradiated GMs and the precursors in Refs. [63—65] can be detected because the GMs were prepared from pre-carbonized EFB whose hemicellulose was almost fully decomposed, and the lignin and cellulose were partially decomposed during pre-carbonization. Comparison of the FTIR spectra of GM-0 and GM-5 shows that irradiation at 5 kGy can slightly change some of the band intensities, shapes and positions, and also produce new bands. Based on the GM-15 and GM-20 spectra, further increases in the dosage may cause further changes in the spectra. A band at ~2160 cm™! was found to be unaffected by the irradiation. This band is associated with C=C (alkynes) and triple bonds, which are not easily broken by the energy of the irradiation used here [66]. Despite these unchanged bands, the other spectral changes shown in Fig. 1 (GM-O—GM-20)
Fig. 1. FTIR spectra for non-irradiated and y-irradiated GMs at different y-radiation doses. The FTIR spectra in the range of wavenumbers from 400 to 4000 cm™! for GM and y-irradiated GM samples are shown in Fig. 1. The patterns of prominent peaks or bands in Fig. 1 for non- irradiated GMs are typical for lignocellulosic materials and are similar to those in the FTIR spectra reported for EFB [59,60], dried date pits [61] and jute fibers [62]. Assignments of these bands to their corresponding functional groups were reported in Refs. {63—65] for EFB samples, and in general, the bands involved C—O and C—H bonds in the macromolecules found in the EFB. Some differences between the FTIR spectra of the non-irradiated GMs and the precursors in Refs. [63—65] can be detected because the GMs were prepared from pre-carbonized EFB whose hemicellulose was almost fully decomposed, and the lignin and cellulose were partially decomposed during pre-carbonization. Comparison of the FTIR spectra of GM-0 and GM-5 shows that irradiation at 5 kGy can slightly change some of the band intensities, shapes and positions, and also produce new bands. Based on the GM-15 and GM-20 spectra, further increases in the dosage may cause further changes in the spectra. A band at ~2160 cm™! was found to be unaffected by the irradiation. This band is associated with C=C (alkynes) and triple bonds, which are not easily broken by the energy of the irradiation used here [66]. Despite these unchanged bands, the other spectral changes shown in Fig. 1 (GM-O—GM-20)
Interlayer spacing, crystallite dimension, and ratios of L./La and L</doo2 for all ACMs Table 1
Interlayer spacing, crystallite dimension, and ratios of L./La and L</doo2 for all ACMs Table 1
Fig. 3. FESEM micrographs for (a) ACM-0, (b) ACM-5, (c) ACM-15 and (d) ACM-20 at low magnification (1.00 K x). Fig. 6 shows the Raman spectra of the ACMs, revealing that all exhibited two sharp bands in the 1100—1800 cm™! region and a broad band in the 2400—3200 cm! region; these are typical bands for the activated carbon |74]. The band intensity of the ACMs from irradiated GMs was less than that of non-irradiated GMs. Note that, for structurally higher ordered graphite, only one band appeared, in the 1100-1700 cm! region. The D band at ~1350 cm™! represents disordered carbon, and the G band at ~1580 cm“! represents or- dered (graphitic) carbon | 75]. The degree of ordering or disordering in the samples is represented by the ratio of the intensities of the D FESEM micrographs of the fractured surface of ACM-0, ACM-5, ACM-15 and ACM-20 samples recorded at low magnification (1.00 K x) are shown in Fig. 3(a)—(d), respectively. All of the mi- crographs, which show the rough surfaces of the grains, rough prain boundaries and smooth surfaces, indicate the porous char- acteristics of the samples made of microstructures with a network of open pores. The microstructure shown in Fig. 3(a) is nearly the same as those in Fig. 3(b)—(d), indicating that the y-irradiation applied to the green monolith did not lead to the changes in the ACM (and activated to prepare activated-carbon-monolith) micro- structure on this scale. FESEM micrographs of the fractured surfaces of all of the samples recorded at higher magnification (15 K x) are shown in Fig. 4(a)—(d), respectively. These high magnification mi- crographs show the microporous microstructure of the ACMs with open pores network distributed evenly throughout the samples. The effects of y-irradiation are still not visible in these micrographs at this scale as all of them look nearly identical. It is possible that the differences between the micrograph shown in Fig. 4(a) and the others could only be observed in micrographs produced at much
Fig. 3. FESEM micrographs for (a) ACM-0, (b) ACM-5, (c) ACM-15 and (d) ACM-20 at low magnification (1.00 K x). Fig. 6 shows the Raman spectra of the ACMs, revealing that all exhibited two sharp bands in the 1100—1800 cm™! region and a broad band in the 2400—3200 cm! region; these are typical bands for the activated carbon |74]. The band intensity of the ACMs from irradiated GMs was less than that of non-irradiated GMs. Note that, for structurally higher ordered graphite, only one band appeared, in the 1100-1700 cm! region. The D band at ~1350 cm™! represents disordered carbon, and the G band at ~1580 cm“! represents or- dered (graphitic) carbon | 75]. The degree of ordering or disordering in the samples is represented by the ratio of the intensities of the D FESEM micrographs of the fractured surface of ACM-0, ACM-5, ACM-15 and ACM-20 samples recorded at low magnification (1.00 K x) are shown in Fig. 3(a)—(d), respectively. All of the mi- crographs, which show the rough surfaces of the grains, rough prain boundaries and smooth surfaces, indicate the porous char- acteristics of the samples made of microstructures with a network of open pores. The microstructure shown in Fig. 3(a) is nearly the same as those in Fig. 3(b)—(d), indicating that the y-irradiation applied to the green monolith did not lead to the changes in the ACM (and activated to prepare activated-carbon-monolith) micro- structure on this scale. FESEM micrographs of the fractured surfaces of all of the samples recorded at higher magnification (15 K x) are shown in Fig. 4(a)—(d), respectively. These high magnification mi- crographs show the microporous microstructure of the ACMs with open pores network distributed evenly throughout the samples. The effects of y-irradiation are still not visible in these micrographs at this scale as all of them look nearly identical. It is possible that the differences between the micrograph shown in Fig. 4(a) and the others could only be observed in micrographs produced at much
Fig. 5. Nitrogen adsorption—desorption isotherms for ACMs from non-irradiated anc y-irradiated GMs at different gamma radiation dosage. The EIS data were recorded as Nyquist plots over the frequency range of 107! to 10° Hz for the ACM-based supercapacitor cells, and these plots are shown in Fig. 7(a). The effects of the dosage on the small semicircle (first segment), Warburg diffusion line (second segment) and capacitive line (third segment) can be clearly
Fig. 5. Nitrogen adsorption—desorption isotherms for ACMs from non-irradiated anc y-irradiated GMs at different gamma radiation dosage. The EIS data were recorded as Nyquist plots over the frequency range of 107! to 10° Hz for the ACM-based supercapacitor cells, and these plots are shown in Fig. 7(a). The effects of the dosage on the small semicircle (first segment), Warburg diffusion line (second segment) and capacitive line (third segment) can be clearly
Fig. 4. FESEM micrographs for (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20 at higher magnification (15 K x).
Fig. 4. FESEM micrographs for (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20 at higher magnification (15 K x).
Pore characteristic parameter values for ACMs from non-irradiated and y-irradiated GMs. Fig. 6. Raman spectra for ACMs from non-irradiated and y-irradiated GMs at different gamma radiation dosage. Table 2
Pore characteristic parameter values for ACMs from non-irradiated and y-irradiated GMs. Fig. 6. Raman spectra for ACMs from non-irradiated and y-irradiated GMs at different gamma radiation dosage. Table 2
The values of Rs, Rp, ESR (EIS), fo, and To for all cells. Table 3
The values of Rs, Rp, ESR (EIS), fo, and To for all cells. Table 3
Specific capacitance values from the EIS, CV and GCD methods for all cells. Table 4
Specific capacitance values from the EIS, CV and GCD methods for all cells. Table 4
Fig. 7. (a) Nyquist plot and (b) Specific capacitance vs. frequency for all cell.
Fig. 7. (a) Nyquist plot and (b) Specific capacitance vs. frequency for all cell.
Fig. 8. Bode plot for all cells (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20.
Fig. 8. Bode plot for all cells (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20.
Fig. 9. (a) Voltammograms for all of the cells and (b) Specific capacitances at different scan rates for all of the cells. It can also be observed that the voltammograms in Fig. 9(a) do not have any peaks, indicating that the supercapacitive behavior is Fig. 9(b) shows the C,p values at different scan rates for all the ACM cells determined from the voltammogram in Fig. 9(a) using equation (5). All cells exhibit a similar decreasing trend in the Cyp values with increasing scan rate. At very low scan rates, the Csp
Fig. 9. (a) Voltammograms for all of the cells and (b) Specific capacitances at different scan rates for all of the cells. It can also be observed that the voltammograms in Fig. 9(a) do not have any peaks, indicating that the supercapacitive behavior is Fig. 9(b) shows the C,p values at different scan rates for all the ACM cells determined from the voltammogram in Fig. 9(a) using equation (5). All cells exhibit a similar decreasing trend in the Cyp values with increasing scan rate. At very low scan rates, the Csp
Fig. 10. Voltammograms for 1-100 mV s“! for all cells, (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20.
Fig. 10. Voltammograms for 1-100 mV s“! for all cells, (a) ACM-O, (b) ACM-5, (c) ACM-15 and (d) ACM-20.
The values of ESR (GCD), specific power (P), and specific energy (E) for all cells compared to the values reported in other works (“Present study, Yaqueous electro- lyte, 7organic electrolyte).
The values of ESR (GCD), specific power (P), and specific energy (E) for all cells compared to the values reported in other works (“Present study, Yaqueous electro- lyte, 7organic electrolyte).
Fig. 11. (a) GCD curves and (b) Ragone plot for all ACMs cells.
Fig. 11. (a) GCD curves and (b) Ragone plot for all ACMs cells.
Fig. 12. Maximum specific power and maximum specific energy data from different references using (a) aqueous and (b) organic electrolytes.
Fig. 12. Maximum specific power and maximum specific energy data from different references using (a) aqueous and (b) organic electrolytes.
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