Application of a Triple-Conducting Heterostructure Electrolyte of Ba₀.₅Sr₀.₅Co₀.₁Fe₀.₇Zr₀.₁Y₀.₁O₃₋δ and Ca₀.₀₄Ce₀.₈₀Sm₀.₁₆O₂₋δ in a High-Performance Low-Temperature Solid Oxide Fuel Cell

Dual-ion electrolytes with oxygen ion and proton-conducting properties are among the innovative solid oxide electrolytes, which exhibit a low Ohmic resistance at temperatures below 550 °C. BaCo₀.₄Fe₀.₄Zr₀.₁Y₀.₁O₃₋δ with a perovskite-phase cathode has demonstrated efficient triple-charge conduction (H⁺/O²–/e–) in a high-performance low-temperature solid oxide fuel cell (LT-SOFC). Here, we designed another type of triple-charge conducting perovskite oxide based on Ba₀.₅Sr₀.₅Co₀.₁Fe₀.₇Zr₀.₁Y₀.₁O₃₋δ (BSCFZY), which formed a heterostructure with ionic conductor Ca₀.₀₄Ce₀.₈₀Sm₀.₁₆O₂₋δ (SCDC), showing both a high ionic conductivity of 0.22 S cm–¹ and an excellent power output of 900 mW cm–² in a hybrid-ion LT-SOFC. In addition to demonstrating that a heterostructure BSCFZY–SCDC can be a good functional electrolyte, the existence of hybrid H⁺/O²– conducting species in BSCFZY–SCDC was confirmed. The heterointerface formation between BSCFZY and SCDC can be explained by energy band alignment, which was verified through UV–vis spectroscopy and UV photoelectron spectroscopy (UPS). The interface may help in providing a pathway to enhance the ionic conductivities and to avoid short-circuiting. Various characterization techniques are used to probe the electrochemical and physical properties of the material containing dual-ion characteristics. The results indicate that the triple-charge conducting electrolyte is a potential candidate to further reduce the operating temperature of SOFC while simultaneously maintaining high performance.