Enhancing the Ionic Conduction of Ceria‐Based Electrolytes for LT‐SOFCs via Entropy Engineering

ABSTRACT Developing alternative electrolytes with enhanced ionic conductivity is crucial to reducing the operating temperature of solid oxide fuel cells (SOFCs) for broader applications. Entropy engineering offers many opportunities for material design, presenting a promising avenue to develop new electrolytes. In this work, two new ceria‐based electrolytes, the medium‐entropy Sm 0.25 La 0.25 Pr 0.25 Ce 0.25 O 2− δ (SLPC25) and low‐entropy Sm 0.05 La 0.05 Pr 0.05 Ce 0.85 O 2− δ (SLPC5) are designed for low‐temperature SOFCs using the entropy engineering strategy, with pure CeO 2 as a reference. It is found that higher configurational entropy leads to enriched oxygen vacancies in the two oxides and thus enhances the ionic transport, which is verified through material characterizations, density functional theory calculations, and cell performance tests. The medium‐entropy SLPC25 exhibits superior cell performance (836 mW cm −2 ) and improved ionic conductivity (0.09 S cm −1 ) at 520°C as compared to those of the low‐entropy SLPC5 and CeO 2 . Further investigation confirms the hybrid proton‐oxygen ion conduction and good fuel cell stability of the SLPC25 electrolyte. This study indicates that higher entropy enhances the ionic conductivity and cell performance of ceria‐based electrolytes. The entropy engineering strategy used here holds significant potential to develop advanced electrolytes for low‐temperature SOFCs.