Exceptionally High‐Performance Reversible Solid Oxide Electrochemical Cells with Ultrathin and Defect‐Free Sm0.075Nd0.075Ce0.85O2‐δ Interlayers

Solid oxide electrochemical cells (SOCs) are promising energy conversion and storage systems owing to their high efficiency and low environmental impact. To lower operating temperatures, the state‐of‐the‐art SOCs with highly active cobaltite‐based oxygen electrodes essentially require doped‐ceria interlayers to avoid undesirable reactions with commercially available zirconia electrolytes. However, the inherent cation interdiffusion between ceria and zirconia materials at high temperatures (>1300 °C) has retarded the construction of highly dense and stoichiometric ceria/zirconia bilayers. This study reports the fabrication of a highly conductive, ultra‐thin (250 nm), and defect‐free Sm0.075Nd0.075Ce0.85O2‐δ (SNDC) interlayer via readily processable gelatin‐assisted deposition. The SOC with the gelatin‐derived SNDC interlayer achieved exceptionally high electrochemical performances both in the fuel cell (≈3.34 W cm‐2) and electrolysis mode (≈2.1 A cm‐2 at 1.3 V) at 750 °C—one of the best records for SOCs with similar configuration to date—along with excellent long‐term durability (1500 h). Mechanistic analysis reveals that the ultra‐thin and dense structure of the SNDC interlayer provides a faster route for oxygen‐ion conduction and more active sites for both oxygen reduction and oxygen evolution reactions at the oxygen electrode/electrolyte interface. The findings suggest that the thin and dense gelatin‐derived SNDC interlayer has great potential for use in high‐performance reversible SOCs. For achieving high performance and durability of solid oxide electrochemical cells, a highly conductivite, ultra‐thin, and defect‐free Sm0.075Nd0.075Ce0.85O2‐δ (SNDC) interlayer via non‐vacuum gelatin‐assisted process is developed. The SNDC interlayer provides a faster route for oxygen ionic conduction and more active sites, resulting in exceptional performances both in the fuel cell (≈3.34 W cm−2) and the electrolysis cell(≈2.1 A cm−2 at 1.3 V) at 750 °C.