Cu, Zn Co-doped ruddlesden-popper La1·2Sr0·8NiO4+δ oxides as high-performance air electrodes of medium-temperature protonic ceramic electrolysis cells

The Ln 2 NiO 4+δ compound (Ln = La, Pr, Nd) finds extensive use as a cobalt-free oxygen electrode material in protonic ceramic electrolysis cells (PCECs) owing to its unique RP-type structure and remarkable catalytic activity . In this study, Cu and Zn co-substitution is employed to fabricate a series of materials, within the La 1 · 2 Sr 0 · 8 Ni 0.5 Cu x Zn 0.5-x O 4+δ system (x = 0.1, 0.2, 0.3, 0.4, denote as LSNCZ14, LSNCZ23, LSNCZ32, and LSNCZ41), and the crystal structure, conductivity, proton absorption and electrochemical properties are comprehensively investigated. The LSNCZ41 exhibits the lowest polarization resistance of 0.83 Ω cm 2 at 600 °C in the symmetric cell. The PCEC single cell incorporating the LSNCZ41 air electrode demonstrates a high electrolysis current density of 1.5 A cm −2 (1.3 V) at 600 °C under 60 % humidity in air, furthermore, negligible degradation is observed under this high current density during electrolysis for over 250 h. These results indicate that LSNCZ41 possesses a higher concentration of interstitial oxygen ions and superior proton absorption capacity , significantly expediting the oxygen reduction reaction (ORR) and ionic transport processes. This material can be considered as a promising candidate for the PCEC air electrodes due to its superior stability in air with high steam content.