## 3 Results
### Electrochemical Performance of the Electrodes
A comparison of the obtained values of polarization resistance for 1050-Fe with the literature data for electrodes of symmetrical electrochemical devicesreveals that it is on a par with the majority of the studied ferrites, with the exception of the most promising materials for symmetrical electrodes based on strontium ferrite-molybdate (Table 3). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Electrode** & **R\({}_{\mathbf{n}}\) in Air** & **R\({}_{\mathbf{n}}\) in H\({}_{\mathbf{2}}\)** & **Ref.** \\ \hline La\({}_{0.6}\)Sr\({}_{0.4}\)FeO\({}_{0.8}\) + 3 wt.\% Fe\({}_{2}\)O\({}_{3}\) & 0.45 & 1.3 & This study \\ Pr\({}_{0.5}\)Sr\({}_{0.6}\)Fe\({}_{0.875}\)O\({}_{0.125}\)O\({}_{3-.8}\) & 1.02 & 1.6 & [66] \\ La\({}_{0.5}\)Ca\({}_{0.1}\)Fe\({}_{0.9}\)Nb\({}_{0.1}\)O\({}_{3-.8}\) & 0.24 & 1.46 & [67] \\ La\({}_{0.5}\)Sr\({}_{0.5}\)Fe\({}_{0.9}\)Mo\({}_{0.1}\)O\({}_{3-.8}\) & - & 3.2 & [68] \\ PrBaMn\({}_{1.5}\)Fe\({}_{0.5}\)O\({}_{5+.5}\) & 0.22 & 0.68 & [69] \\ La\({}_{0.3}\)Sr\({}_{0.7}\)Fe\({}_{0.9}\)Ti\({}_{0.1}\)O\({}_{3-.8}\) & 0.022 & 0.15 & [70] \\ La\({}_{0.8}\)Sr\({}_{1.2}\)Fe\({}_{0.5}\)Co\({}_{0.1}\)O\({}_{4\pm 6}\) & 0.29 & 1.14 & [71] \\ LaSr\({}_{2}\)Fe\({}_{2}\)CrO\({}_{0.8}\) & 0.29 & 0.57 & [72] \\ PrBaFe\({}_{0.6}\)Se\({}_{0.2}\)O\({}_{35+.8}\) & 0.05 & 0.18 & [73] \\ La\({}_{0.8}\)Sr\({}_{2}\)Fe\({}_{0.5}\)O\({}_{5-.5}\) & 0.48 & 0.92 & [74] \\ Sr\({}_{2}\)Fe\({}_{1.4}\)Nb\({}_{0.1}\)Mo\({}_{0.5}\)O\({}_{6-.8}\) & 0.098 & 0.22 & [75] \\ Pr\({}_{0.6}\)Sr\({}_{0.4}\)Fe\({}_{0.7}\)Ni\({}_{0.2}\)Mo\({}_{0.1}\)O\({}_{3-.8}\) & 0.5 & 0.2 & [76] \\ Sr\({}_{2}\)Fe\({}_{1.4}\)Ni\({}_{0.1}\)Mo\({}_{0.5}\)O\({}_{6-.8}\) & - & 0.78 & [77] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Polarization resistances (\(\Omega\) cm\({}^{2}\)) of various symmetrical electrodes in contact with LSGM electrolyte at 800 \({}^{\circ}\)C.  
Figure 5: Temperature dependences of the polarization resistance of electrodes in air (**a**). Impedance spectra of electrodes in air at 800 \({}^{\circ}\)C (**b**). DRT functions calculated from the impedance spectra (**c**). SEM images of surface of 1050-Cu and 1150-Cu samples (**d**). A comparison of the electrochemical impedance spectra of 1050-Fe in oxidizing and reducing atmospheres reveals significant differences (Figure 7a). The DRT functions calculated from these spectra revealed that the primary discrepancies in the mechanisms of hydrogen oxidation and oxygen reduction reactions are associated with the emergence of a high-frequency process of considerable intensity in the reducing atmosphere. In contrast, the remaining peaks were previously observed on the DRT function for the oxidizing atmosphere and exhibited only minor alterations following the transition to the reducing atmosphere. A consideration of the DRT functions for all the studied samples in the atmosphere of wet hydrogen reveals that, according to a rough approximation, the mechanism of hydrogen reduction at all the studied electrodes is essentially the same. This is in contrast to the air atmosphere, where shifts of peaks or the appearance of new ones are observed. Instead, in the wet hydrogen atmosphere, only changes in peak intensity are evident (Figure 7b). The high-frequency peak is characterized by the greatest intensity changes. Given the relaxation frequency of this peak, it can be posited that this process represents a stage of charge transfer at the triple-phase boundary. This assertion is indirectly corroborated by the capacitance value calculated from the impedance spectrum, which is approximately \(5\times 10^{-6}\) F/cm\({}^{2}\). This stage is localized at the three-phase electrolyte/electrode/gas boundary. It can therefore be reasonably assumed that with the increase in the sintering temperature, there is an increase in the area of contact between the electrolyte and the electrode, and the extent of the triple-phase boundary decreases. This leads to an increase in the resistance of this stage. As illustrated in Figure 5c in an oxidizing atmosphere, this step in the DRT function is absent.