Electrochemical and microstructural characterization of the high-entropy perovskite La0.2Pr0.2Nd0.2Sm0.2Sr0.2CoO3-δ for solid oxide cell air electrodes

Strontium segregation (coupled to phase decomposition and impurity poisoning) and electrode delamination are two of the most important degradation mechanisms currently limiting the long-term stability of solid oxide fuel cell and electrolysis cell (SOFC and SOEC) air electrodes. The present study aims to demonstrate that air electrodes made of entropy-stabilized multi-component oxides can mitigate these degradation mechanisms while providing excellent cell performance. A SOEC utilizing La_0.2Pr_0.2Nd_0.2Sm_0.2Sr_0.2CoO_3-δ (LPNSSC) as an air electrode delivers −1.56 A/cm² at 1.2 V at 800°C. This performance exceeds that of a commercial cell with La_0.6Sr_0.4CoO_3-δ (LSC) air electrode, which reaches −1.43 A/cm². In a long-term electrolysis test, the LPNSSC cell shows stable performance during 700 h, while the LSC cell degrades continuously. Post-mortem analyses by scanning electron microscopy-energy dispersive X-ray spectroscopy indicate complete delamination of the LSC electrode, while LPNSSC shows excellent adhesion. The amount of secondary phases formed (esp. SrSO₄) is also much lower in LPNSSC compared to LSC. In conclusion, the high-entropy perovskite LPNSSC is a promising option for air electrodes of solid oxide cells. While LPNSSC can compete with ‒ or even outperform ‒ LSC air electrodes in terms of electrochemical performance, it could be particularly advantageous in terms of long-term stability in SOEC mode.