# Exploring CeO\({}_{2}\)-Doped Co/SBA-15 Catalysts for Acetic Acid Oxidative Steam Reforming
## 3 Results and Discussion  
### Catalyst Characterization  
The elemental composition and the textural characteristics of the catalysts synthesized in the current research are summarized in Table 1. Concerning metal loadings calculated via ICP-OES, the calcined catalysts have Ce and Co contents nearing the nominal value established at the SBA-15 and Ce/SBA-15 impregnation, respectively. Figures 2A and S1 show the N2 physisorption isotherms of the calcined catalysts and supports, respectively. These isotherms exhibited a type IV isotherm curve with an H1-type hysteresis loop according to the IUPAC classification, which is typical for mesoporous material consisting of well-defined cylindrical pore channels [40]. These results demonstrate that the characteristic porous structure of bare SBA-15 was preserved  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Sample** & **Ce 1 ** & **Co 2 ** & **S2 ** & **Np 3 ** & **D 5 [FOOTNOTE:5]Footnote 5: 5  
after the support modification with ceria and the cobalt active phase incorporation. Notably, some differences in the isotherm shape can be appreciated with the increase in Ce content, indicating a slight modification of the mesoporous structure. This effect is particularly evident for Co/20 CeO\({}_{2}\)-SBA-15 and Co/30 CeO\({}_{2}\)-SBA-15 samples because of their higher Ce content, resulting in 38.2% and 50.8% decreases in BET surface area, respectively, compared to the Co/SBA-15 catalyst. In line with this assumption, the pore volume, BET surface area, and mean pore diameter displayed in Table 1 and Table S1, corresponding to catalyst and supports, respectively, became smaller as the CeO\({}_{2}\) amount increased, which can be ascribed to partial filling of SBA-15 channels. Similar behavior was observed after cobalt incorporation into the ceria-modified silica supports. The UV-Vis diffuse reflectance spectra of the supports are shown in Figure S2. The UV-Vis spectra of the CeO\({}_{2}\)-SBA-15 supports show a broad absorption band centered at about 288 nm, ascribed to charge transfer transitions from O\({}^{2-}\) to Ce\({}^{4+}\)[41; 42]. An additional shoulder around 255 nm is noted in particular for the 5 CeO\({}_{2}\)-SBA-15 support, possibly indicating the presence of Ce\({}^{3+}\) species. Band gap energy was estimated by the Tauc method, calculated from the intercept with the abscissa in a linear regression of the (F(R)\(\cdot\)h\(\cdot\))\({}^{1/\text{n}}\) vs. h\(\cdot\) representation, considering a direct electronic transition (n = %) [43] (Figure S3). The obtained values exhibit a slight variation, 3.7 eV (5 CeO\({}_{2}\)-SBA-15), 3.5 eV (10 CeO\({}_{2}\)-SBA-15), 3.6 eV (20 CeO\({}_{2}\)-SBA-15), and 3.7 eV (30 CeO\({}_{2}\)-SBA-15). Such differences indicate possible alterations in the electronic structure of the supports, linked to the presence of structural defects. These defects are probably caused by the formation of oxygen vacancies. In particular, the decrease in the band gap observed in the 10 CeO\({}_{2}\)-SBA-15 and 20 CeO\({}_{2}\)-SBA-15 supports is likely related to an improved density of oxygen vacancies [44]. The crystalline phases of ceria and cobalt oxides supported on SBA-15 material were analyzed by XRD, and their diffraction patterns are illustrated in Figure 2B. All the catalysts show a broad peak between 20 and 30\({}^{\circ}\), ascribed to the amorphous SiO\({}_{2}\) on the SBA-15 framework [45]. The intensity of the peak becomes smaller as the CeO\({}_{2}\) content increases. Peaks related to the Co\({}_{3}\)O\({}_{4}\) cubic phase (JCPDS 01-071-4921) appear in all the patterns of the  
Figure 2: N\({}_{2}\) physisorption isotherms at 77 K (**A**) and XRD diffraction patterns (**B**) of calcined catalysts. materials after calcination, showing reflections at 20 = 31.2, 36.8, 44.8, 59.5, 65.4, and 77.7\({}^{\circ}\), referring to the (220), (311), (400), (511), (440), and (533) diffraction planes, respectively.