## 3 Results and Discussion  
Figure 1 shows the Raman (a) and FTIR (b, c) spectra for the six RFX-Cs samples. Figure 1a shows two characteristic Raman spectra peaks at 1355 and 1589 cm\({}^{-1}\), which refer to disorder peak (D-band) and graphitic peak (G-band), respectively. The intensity ratio of the D-band to the G-band (i.e., \(I_{\text{D}}\)/\(I_{\text{G}}\) ratio) helps to estimate the defects and disorders of RFX-Cs samples [25]. The results of \(I_{\text{D}}\)/\(I_{\text{G}}\) ratios, along with CHNS/O analyses and pore characteristics of RFX-Cs-0 through RFX-Cs-5, are presented in Table 2. Overall, it is observed from Table 2 that increasing the concentration of Cs into RFX leads to increasing \(I_{\text{D}}\)/\(I_{\text{G}}\) ratios, which indicates a significant increase of disorders and defects inside the structures of RFXs (even though the added amounts of Cs is very minor). Furthermore, increasing the concentration of Cs into the RFX results in slightly reducing concentrations of carbon and hydrogen, and slightly increasing concentration of nitrogen. The presence of Cs into RFX affects its pore structure, pore volume, surface area, crystal order/disorder, N\({}_{2}\) adsorption capacity, and average pore width. Moreover, the data listed in Table 2 shows that the adsorption capacities of RFX-Cs-1 and RFX-Cs-2 samples are low. This is due to lowering their total pore volumes. Figure 1b exposes the whole scale of FTIR spectra from 4000 to 400 cm\({}^{-1}\), and Figure 1c shows a zoomed-in range from 1700 to 500 cm\({}^{-1}\). The peaks at 2935, 2870, and 1477 cm\({}^{-1}\) (related to the CH\({}_{2}\) stretching and bending vibrations) were observed in RFX-Cs-0 (curve 1), but not in other samples. The broadband at 3302 cm\({}^{-1}\) indicates the aromatic OH group of resorcinol, whereas that at 1607 cm\({}^{-1}\) refers to the aromatic ring stretches. The medium-to-weak peak appearing at 1218 cm\({}^{-1}\) refers to that of methylene ether linkages between resorcinol rings [26]. Curves 2 through 6 correspond to the presence of Cs into the matrix of RFX. The dotted blue lines crossing the peak at \(\sim\)1153 cm\({}^{-1}\) is for asymmetric stretch of C-O-C, and that at 1298 cm\({}^{-1}\) is for the C-N stretching vibration of type I amine. The peak at 1298 cm\({}^{-1}\) that appeared for RFX-Cs-0 started to diminish and became shoulder peak when adding Cs into the structure of RFX. On the other hand, a new small peak appears at 995 cm\({}^{-1}\) in curves 2 to 6 (crossed via dotted blue lines), which is not found in pure RFX (i.e., sample RFX-Cs-0, represented by curve 1). Therefore, changes occurred in the structure of RFX by adding Cs even in minor amounts. \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline
**Sample** & \(\mathbf{\text{d}}_{\text{D}}\mathbf{\text{d}}_{\text{C}}\)1 [FOOTNOTE:1]Footnote 1: values determined from Raman spectra. \(\mathbf{\text{b}}\) Values determined from Micromerities ASAP [FOOTNOTE:1]Footnote 1: Values determined from Raman spectra. \(\mathbf{\text{b}}\) Values determined from Micromerities ASAP [FOOTNOTE:1]Footnote 1: Values determined from Micromerities ASA  
Figure 2a,b exhibits the XRD patterns and TGA thermograms, respectively, for the six RFX-Cs samples. In Figure 2a, the full width at half-maximum (FWHM) peeks of XRD profiles was used. It was observed that the intensity of XRD peaks decreases by adding Cs to the RFX. For instance, the intensity decreased from 1998 to 1480 cps when comparing RFX-Cs-0 to RFX-Cs-5, respectively, which corresponds to a decrease of \(\sim\)26% in intensity. This observation aligns with the Raman results, which indicate an increasing disorder with the addition of Cs into the RFX-Cs matrix. Furthermore, the XRD peak of RFX-Cs-0 at 15.89\({}^{\circ}\) shifts gradually to 19.75\({}^{\circ}\) for RFX-CS-5. This shift is due to the insertion of Cs into the RFX matrix. Figure 2b exposes that the presence of Cs into the RFX matrix affects the thermal stability noticeably.