## 4 Results and Discussion  
Nitrogen adsorption-desorption isotherms for pristine and modified carbon samples are shown in Figure 6. All recorded isotherms are very similar and conform to the IUPAC classification of Type IV. The observed hysteresis loop beyond the P/P\({}_{0}\) threshold of 0.43 signifies the occurrence of capillary condensation, providing evidence for the presence of mesopores. The pronounced incline at lower relative pressures signifies the presence of supplementary micropores. The mesopores enhance the mass transfer of adsorbate molecules, proving advantageous in sorption applications. The hysteresis loop has been identified as H4. Hysteresis loops of type H4 are commonly encountered in complex materials that consist of both micropores and mesopores. It is characteristic of activated carbons. The textural parameters of pristine and modified carbon samples are listed in Table 1.  
The BET surface area of the starting materials was equal to 1177 m\({}^{2}\)/g, the total pore volume was 0.631 cm\({}^{3}\)/g, and the micropore volume was 0.383 cm\({}^{3}\)/g. The values of the textural parameters after spark discharge treatment increased slightly, no more than 1.4%. After barrier discharge, the textural parameters decreased very slightly, no more than 0.5%. After plasma treatment, the nitrogen content increased by 10% for both samples. \begin{table}
\begin{tabular}{c c c c c} \hline
**AC** & **BET** & **V\({}_{\text{tot}}\)** & **V\({}_{\text{micro}}\)** & **C\({}_{\text{N2}}\)** \\  & **m\({}^{2}\)/g** & **cm\({}^{3}\)/g** & **cm\({}^{3}\)/g** & **wt \%** \\ \hline DT0 & 1177 & 0.631 & 0.383 & 0.9 \\ DT0\_1 & 1164 & 0.622 & 0.380 & 1.0 \\ DT0\_2 & 1181 & 0.632 & 0.385 & 1.0 \\ \hline \end{tabular}
\end{table} 
Table 1: Textural properties and nitrogen content of pristine (DT0) and modified by N2 plasma samples (DT0_1, DT0_2). Figure 6: N2 adsorption-desorption isotherms at 77 K for pristine (DT0) and modified by N2 plasma samples (DT0_1, DT0_2). The DFT model was employed to derive the pore size distribution of the AC. The results are presented in Figure 7. Evidently, all examined samples displayed a similar pore size distribution, demonstrating comparable structural characteristics with abundant micropores and mesopores. The results shown in Figure 7 are consistent with the values presented in Table 1.  
The X-ray diffraction profiles of pristine plasma-activated carbons and those modified by cold nitrogen are presented in Figure 8. The profiles are very similar. All the samples demonstrate extremely wide diffraction peaks, and the lack of a distinct peak indicates a primarily amorphous structure. The XRD patterns of all AC typically show three broad bands due to reflections from the following planes (002)--2\(\theta\) = 24.6\({}^{\circ}\), (10)--2\(\theta\) = 43.4\({}^{\circ}\), and (11)--2\(\theta\) = 73.7\({}^{\circ}\). The first one is associated with the pseudocrystallite height (Lc), and the second one is associated with the pseudocrystallite width or average hexagonal carbon layer diameter (La). Both parameters can be obtained using the Scherrer equation, as follows:  
Figure 8: XRD pattern of pristine plasma samples (DT0) and those modified by N2 (DT0_1, DT0_2). Figure 7: Pore size distribution curves of pristine (DT0) and modified by N\({}_{2}\) plasma samples (DT0_1, DT0_2). \[L=\frac{K\cdot\lambda}{\beta\cdot cos(\theta)} \tag{8}\]  
where:  
\(\theta\)--angle of incidence  
\(\lambda\)--wavelength of characteristic line utilized in X-ray spectrometry, equal to 0.154 nm for CuK\(\alpha\)  
\(\beta\)--width at half peak height  
The stacking size Lc is calculated on the basis of data related to the first peak (\(20=24.6^{\circ}\)) and K equal to 0.9. The pseudocrystallite width (La) is calculated on the basis of data related to second peak (\(20=43.4^{\circ}\)) and K equal to 1.94 [40].