## 3 Results and Discussion  
### Analysis of Weight Increase Rate and Oxygen Functional Groups after Stabilization  
Comparing the weights of SP220 before and after stabilization (Table 1) demonstrated that the weight increased during all the stabilization processes. The weight at 260 \({}^{\circ}\)C increased to 103.17%, indicating an excellent weight gain. The thermal weight analysis results for SP220 are shown in Figure 1, demonstrating that the SP220 has better thermal stability than other conditions at 260 \({}^{\circ}\)C. This confirms that the properties of thermoplasticity change due to the thermosetting during the process of increasing the weight and re-coagulation because the pitch melts at a certain temperature and forms an oxygen functional group. However, the thermal stability was lower than 260 \({}^{\circ}\)C at 280 \({}^{\circ}\)C because the average melting point was 220 \({}^{\circ}\)C; therefore, the pitch significantly melted as it could not withstand the temperature. The FT-IR spectrum of the pitch obtained via the stabilization process is shown in Figure 2. In the SP220 samples, the peaks of the carboxylic group, aliphatic C-H, aromatic CH\({}_{2}\), and aromatic C-H were observed at approximately 3045, 2915, 1470, and 900-700 cm\({}^{-1}\), respectively. In addition, CH\({}_{3}\) and CH\({}_{2}\)/CH\({}_{3}\) were identified at approximately 2960 and 2850 cm\({}^{-1}\)[27]. A higher stabilization temperature resulted in weaker or fewer peaks. This confirmed that the bond between carbon and hydrogen was broken depending on the temperature and that there was an oxygen functional group on the spot. Therefore, we determined that the sample stabilized at 260 \({}^{\circ}\)C would be the most suitable. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **SP220-220** & **SP220-240** & **SP220-260** & **SP220-280** \\ \hline Weight before & 5.92 & 5.80 & 5.88 & 6.17 \\ stabilization (g) & 6.03 & 5.97 & 6.15 & 6.43 \\ Weight & 0.11 & 0.17 & 0.27 & 0.26 \\ Difference (g) & 101 & 102 & 103 & 103 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Pitch weight comparison before and after stabilization. In this study, significant differences were observed in the surface area, total pore volume, micropore volume, and micropporosity among the three studied samples. These variations can be attributed to the differences in the activation ratios used during the chemical activation process. Specifically, the pitch-to-KOH ratio plays a crucial role in determining the extent of pore development. The results of the specific surface area, pore volume, and microporovosity of pitch-based activated carbon produced by chemical activation are shown in Table 2. Based on the weight ratio, the overall specific surface area was the highest at 3330 m\({}^{2}\)/g at a ratio of 1:4. The specific surface area decreased to 2999 m\({}^{2}\)/g at a ratio of 1:8 because pitch apparently collapsed owing to the excessive activation. This phenomenon is likely due to the over-penetration of KOH into the carbon structure, which, at higher concentrations, can cause the breakdown of the microporous network. Therefore, the differences in surface properties among the samples are directly related to the degree of chemical activation and the corresponding structural changes induced during the process. The remaining adsorption isotherm graphs, except for 1:8, are represented in the form of type I among the six graphs of the International Union of Pure Applied Chemistry (IUPAC). Many micropores were involved in adsorption, with particles smaller than 2 nm. The decrease in the number of micropores indicates an increase in the number of mesopores and macropores. The smaller specific surface area observed for the 1:8 condition, despite higher adsorption isotherms, is attributed to the increased relative volume of mesopores and macropores, likely due to the overactivation with KOH. Figure 4: SEM scanning images of the AC pellet: (**a**) SP220 1:1, (**b**) SP220 1:4, (**c**) SP220 1:8. Figure 3: A BET image of SP220 activation.