## 3 Results
### Xps
The fitting of the spectra into components was carried out taking into account the position of the states for Mn(III) and Mn(IV) oxides, which are about 641.3 and 642.5 eV, respectively [52]. It was also taken into account that in the high-energy region of the Mn2p3/2 spectrum for manganese oxides, states are observed due to the effect of multiplet splitting and also observed in the PE spectra of other transition metals [52; 53]. We approximated these states using a component with a binding energy of about 645 eV (indicated in the figure as satellite). The relative share of this component in all spectra was about 14% and was not taken into account in the final assessment of the content of various manganese oxides (Mn(III) and Mn(IV)) in the samples. The maximum of the Mn 2p3/2 in the PE spectrum of the Mn-0 composite (Figure 4a) is located at a binding energy of 642.2 eV. The approximation result shows that Mn(IV) oxide predominates--the relative proportion of the corresponding component is 59.7% (Table 3). In the Mn2p PE spectrum of the Mn-580 composite (Figure 4b), the maximum is significantly shifted towards low-binding energies (the offset is \(-\)0.6 eV), which is most likely due to a significant increase in the proportion of Mn(III) oxide in the composite. Apparently, when the composite was annealed in an inert atmosphere or vacuum at a given temperature, Mn(IV) oxide disproportionated to form Mn(III) oxide [23; 54; 55]. In the Mn2p PE spectra of the heat-treated composites, after the addition of rhenium oxide (Figure 4c,d), the maximum shifts to high-binding energies (relative  
Figure 3: C1s (**a**) and O1s (**b**) PE spectra of MWCNTs and composites. to the spectrum of the Mn-580 composite), and its width increases significantly (Table 3). The result of the spectrum approximation showed that after the addition of rhenium in the composite, the proportion of Mn(III) oxide increases. At the same time, the relative areas of the components corresponding to Mn(III) and Mn(IV) oxides in the Mn-580 + Re and Mn-700 + Re composites have fairly close values with a slightly higher Mn(IV) content in the Mn-580 + Re composite. Figure 4: Mn 2p PE spectra of the composites: Mn-0 (**a**), Mn-580 (**b**), Mn-580 + Re (**c**), Mn-700 + Re (**d**). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Composite**} & \multirow{2}{*}{**Peak Position, eV**} & \multirow{2}{*}{**FWHM, eV**} & \multicolumn{2}{c}{**Relative Area of the Component, \%**} \\ \cline{3-4}  & & & **Mn(III)** & **Mn(IV)** \\ \hline Mn-0 & 642.2 & 2.93 & 40.3 & 59.7 \\ Mn-580 & 641.6 & 2.74 & 69.0 & 31.0 \\ Mn-580 + Re & 642.0 & 3.06 & 45.1 & 54.9 \\ Mn-700 + Re & 641.9 & 2.99 & 47.5 & 52.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of the analysis of Mn 2p PE spectra of composites. In the Re4f PE spectrum of the Re-360 composite (Figure 5a), states with maxima at binding energies of 43.6 and 46.0 eV are observed, as well as states with maxima at binding energies of 46.5 and 48.9, which according to [50] correspond to ReO\({}_{2}\) and Re\({}_{2}\)O\({}_{7}\) oxides, respectively. This fact is also confirmed by the pieces of work in [39; 56; 57], where rhenium oxides (IV) and (VII) were obtained under similar conditions. It is important to note that in the temperature range of 300-400 \({}^{\circ}\)C, the probability of direct decomposition of ammonium perhenate into rhenium hepoxide is unlikely due to positive Gibbs free energy [57]. In view of this, we believe that Re\({}_{2}\)O\({}_{7}\) is formed through the formation of an intermediate product of the ReO\({}_{3}\) reaction from ammonium perhenate having negative Gibbs free energy, followed by disproportionation to Re\({}_{2}\)O\({}_{7}\) + ReO\({}_{2}\)[39]. In the spectra of Mn-580 + Re and Mn-700 + Re composites (Figure 5b,c), only states corresponding to Re\({}_{2}\)O\({}_{7}\) oxide are observed, and in the high-energy region of the spectrum there is an overlap of the Re4f and Mn3p ranges.