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

Abstract

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.