Homotypic perovskite heterostructures of Sr0.95Ce0.05CoO3-δ–BaZr0.1Ce0.7Y0.2O3-δ: Dual-function electrolytes for ionic conductivity enhancement and electron confinement

Interfacial heterojunction effects have been widely recognized as a critical strategy to enhance ionic conductivity in low-temperature solid oxide fuel cells (LT-SOFCs). However, existing studies predominantly focus on heterostructures composed of materials with distinct crystal structures. In contrast, this study presents a novel composite electrolyte comprising two perovskite-type oxides with analogous crystal structures: Sr 0.95 Ce 0.05 CoO 3-δ (SCC) and BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY). Microstructural characterizations reveal that nanoscale interfacial contacts and atomic-level continuity are established by coating BZCY grains onto the surfaces of SCC grains at various mass ratios. The formed homotypic heterostructure enriches the oxygen vacancy concentration by 12.4% relative to that of BZCY, which can be attributed to the lattice dislocations at the SCC–BZCY interface. The fuel cell employing the optimal 2SCC–8BZCY composite electrolyte achieves a peak power density of 914 mW cm −2 at 520 °C, 1.8 times higher than that with BZCY electrolyte (517 mW cm −2 ). The corresponding electrolyte ionic conductivity reaches 0.208 S cm −1 , 2.15 times higher than that of BZCY electrolyte. The superior electrochemical performance of the composite cell can be attributed to the formation of a heterojunction and generated built-in electric field (BIEF) at the SCC–BZCY interface, which suppresses electronic conduction meanwhile boosts ionic conduction, as confirmed by the band structure analysis.