## 3 Results and Discussion
### The Characterization of the Reduced Catalysts  
Since active sites for the CSMR reaction are Ni\({}^{0}\) crystallites, the dispersion of the catalysts and their stability to sintering during activation of the NiO in a reducing atmosphere were examined by XRD (Figure 3, Table 3). The XRD patterns of all catalysts reduced at 800 \({}^{\circ}\)C for 2 h in an atmosphere of 30 vol.% H\({}_{2}\)/He are shown in Figure 3. The as-reduced catalysts showed similar diffractograms compared to the pristine catalysts, while the corresponding peak intensities for cerium oxide were narrower, indicating an increase in crystallinity and nanoparticle size after reduction. The peak positions at 31.1\({}^{\circ}\) and 44.5\({}^{\circ}\) revealed the NaCl phase (ICSD 44277) in the reduced C catalyst. The phase composition of the catalysts after activation in an atmosphere of 30 vol.% H\({}_{2}\)/He depended on the method of sample synthesis (Table 3). Ni\({}^{2+}\) species in the C catalyst could not be reduced at the pretreatment of 800 \({}^{\circ}\)C under the 30 vol.% H\({}_{2}\)/Ar atmosphere. [PERSON] et al. found that chlorine ions prevented the reduction of Ni\({}^{2+}\) ions and suppressed the adsorption of CO\({}_{2}\)[54]. The activation of the A-series catalysts led to the reduction of the NiO phase and the formation of the Ni\({}^{0}\) phase (ICSD 646090) (Table 3, Figure 3). When comparing data for the Ni/CeMg samples reduced at 800 \({}^{\circ}\)C, the samples of the A-P-O and A-S-O series were characterized by a lower dispersion of Ni\({}^{0}\), calculated from the Ni(111) phase at 44.3\({}^{\circ}\) using the Debye-Scherrer equation. Apparently, the Ni\({}^{0}\)-Ce\({}_{0.5}\)Mg\({}_{0.5}\)O\({}_{1.5}\) interaction (MSI) was much weaker for the A-P-O and A-S-O samples, which ensured the agglomeration and reduction of Ni\({}^{2+}\) in the process of their activation. The XRD study at an increase in temperature up to 800 \({}^{\circ}\)C showed that the resistance to sintering was higher in the case of the A-S-V samples. Figure 2: X-ray diffraction patterns of the as-prepared catalysts calcined at 500 \({}^{\circ}\)C. 1—Ni/CeMg-C-S-O; 2—Ni/CeMg-A-S-O; 3—Ni/CeMg-A-S-V; 4—Ni-Pd/CeMg-A-S-V; 5—Ni/CeMg-A-P-O. To understand the effect of the support precursor, the activation mode, and the active component composition on the catalytic properties, an analysis of XPS spectra was carried out. Survey XPS spectra revealed the presence of Ni, Ce, Zr, and O for all prepared catalysts (Figure S5). In addition, the C catalyst contained Cl, which appeared as a peak at 199.4 _eV_. This was consistent with diffraction patterns of catalysts reduced and calcined at 800 \({}^{\circ}\)C showing the peak of NaCl at 31.6\({}^{\circ}\) and 45.3\({}^{\circ}\). According to the XPS study, Ni existed in the form of Ni\({}^{2+}\), which was confirmed by peaks at binding energies BE(Ni2P\({}_{1/2}\)) = 873.9 eV and BE(Ni2P\({}_{3/2}\)) = 856.7 eV and a shake-up satellite at about 861-862 eV (Figure S6). For the A catalysts, the peaks centered at 852.6 eV were assigned to Ni\({}^{0}\). Ni was present as Ni\({}^{2+}\) in the reduced C catalysts. This was in good agreement with the XRD data (Table 4). In addition, the surface concentration of nickel in this catalyst was much lower than in catalysts A. For Ni/CeMg-A-P-O, the ratio Ni/Ce was greater (Table 4) and the peak position of Ni\({}^{2+}\) shifted to a lower BE compared to that of Ni-Pd/CeMg-A-S-V, Ni/CeMg-A-S-V, and Ni/CeMg-A-S-O (Figure S6), indicating that the polychol method ensured the weakening of the interaction between the Ni\({}^{2+}\) and the Ce\({}_{0.5}\)Mg\({}_{0.5}\)O\({}_{1.5}\) support and the location of nickel species on the surface. Spectra of Ce3d core (Figure 4) contained two sets of spin-orbit multiplets corresponding to a 3d\({}_{5/2}\) and 3d\({}_{3/2}\) ionization, respectively.