and ceramic perovskite-like oxygen electrode. If properly designed, the cell may operate alternately in fuel cell and electrolyzer regimes (reversible solid oxide cell or rSOC) [6]. The SOEC technology is currently at moderate TRL (technology readiness level), and long-term degradation remains one of the main challenges obstructing the widespread adoption of solid oxide electrolysis cells as practical hydrogen generation systems. A specific degradation mechanism in SOEC relates to delamination of the oxygen electrode and accompanying processes occurring at the electrolyte/oxygen electrode interface [3; 7; 8; 9]. The mechanisms of delamination were studied for LSM (La\({}_{1-x}\)Sr\({}_{x}\)MnO\({}_{3-8}\)), LSFC (La\({}_{1-x}\)Sr\({}_{x}\)Fe\({}_{1-y}\)Co\({}_{y}\)O\({}_{3-8}\)), and other perovskite-type oxygen electrodes. The common view is that high oxygen partial pressure buildup within the pores, grain boundaries and other defects in the near-interface electrolyte layer and also at the electrode/electrolyte interface under anodic polarization results in intergranular fractures in the electrolyte surface layer and cracking and delamination at the electrode/electrolyte interface [7; 8; 9]. These irreversible degradation processes are contributed or promoted by the interdiffusion of cations with the formation of undesired phases at the interface, insufficient ionic conductivity, and, consequently, the electrochemical activity of the oxygen electrode, and other factors. The electrochemical studies of rSOCs operation revealed that the degradation occurring at the electrolyte/oxygen electrode interface can be slowed down if a cell operates in a reversible SOEC/SOFC regime and that the degradation occurring in the SOEC regime may be partially recovered during the operation in SOFC mode if the cycles duration does not exceed a certain limit [8; 9; 10]. Although further long-term studies and fundamental understanding of this phenomenon are still required, the experimental observations raise prospects to halt degradation and to develop self-healing approaches based on reversible SOEC/SOFC cycles [11]. One possible approach may be based on the introduction of redox-active components with oxygen storage capacity in the form of inclusions into the surface layer of solid electrolyte or as a thin buffer layer at the electrode/electrolyte interface capable of oxygen uptake under anodic polarization to prevent oxygen pressure build-up and reverting to oxygen loss in fuel cell mode. To enhance the chemical and thermomechanical compatibility, these components can be based on zirconia co-substituted by yttrium and variable-valence cations such as manganese [12; 13; 14; 15] or praseodymium. Prasedymium oxide exhibits rich redox chemistry under oxidizing conditions. The average oxidation state of praseodymium cations in PrO\({}_{y}\) at atmospheric oxygen pressure varies between 3.67+ in Pr\({}_{6}\)O\({}_{11}\) at temperatures below \(\sim\)350 \({}^{\circ}\)C to 3+ in Pr\({}_{2}\)O\({}_{3}\) above 1300 \({}^{\circ}\)C [16; 17; 18]. Under equilibrium conditions at elevated temperatures (\(>\)1500 \({}^{\circ}\)C), praseodymium substitutes into the zirconia lattice with the formation of solid solutions based on monoclinic ZrO\({}_{2}\), cubic ZrO\({}_{2}\) and pyrochlore-type Pr\({}_{2}\)Zr\({}_{2}\)O\({}_{7}\)[19; 20; 21; 22]. Increasing the praseodymium content in (ZrO\({}_{2}\))\({}_{1-x}\)(PrO\({}_{y}\))\({}_{x}\) was reported to enhance ionic conductivity, with a maximum observed at \(x\) = 0.25, and to increase \(p\)-type electronic conductivity [23; 24]. The compositions containing 9-40 mol.% of PrO\({}_{y}\) were found to be predominantly oxygen ionic conductors with an ionic contribution to the total conductivity of \(\geq\)80% [23; 24]. Metastable cubic fluorite-type ZrO\({}_{2}\)-PrO\({}_{y}\) solid solutions can also be prepared at moderate temperatures. [PERSON] et al.