Perovskite/Ruddlesden-Popper composite fuel electrode of strontium-praseodymium-manganese oxide for solid oxide cells: An alternative candidate

Ni migrates from cermet fuel electrodes in SOECs at high overpotentials, prompting interest in alternative electrode materials. Ni-free perovskites with mixed ionic and electronic conductivity are being developed as substitutes for Ni-YSZ- or Ni-CGO-cermet fuel electrodes. However, some perovskite electrodes exhibit poor electrocatalytic activity during steam electrolysis. This study focuses on the synthesis, phase evolution, and cation oxidation state of Sr0.5Pr0.5MnO3 (SPM) perovskite under oxidizing and reducing atmospheres. The electrochemical performance of the SPM electrode is investigated at different steam concentrations (3–50% H2O in H2). Rietveld refinement reveals a phase transformation from Pm-3m (221) to I4/mmm (139) in humidified 5% H2 in N2 gas at 800 °C. XPS measurements indicate that the I4/mmm (139) structure contains more oxygen vacancies, enhancing ionic conductivity and electrocatalytic activity. At 610 ◦C, the SPM electrode with the Pm-3m (221) space group exhibits a low polarization resistance of 0.173 Ω cm2 in 50% H2O in H2 gas. However, forming a Ruddlesden-Popper structure increases polarization resistance at higher temperatures due to a low-frequency reaction. Overall, the SPM electrode shows promising electrocatalytic activity across a wide range of oxygen partial pressure, making it a potential fuel electrode in SOECs.