MgO-engineered depletion regions in Sm0.2Ce0.8O1.9/ YBaCo4O7+δ electrolytes boosting low-temperature SOFCs performance

The study presents a novel heterostructure electrolyte composed of fluorite-structured Sm 0.2 Ce 0.8 O 1.9 (SDC), hexagonal YBaCo 4 O 7+δ (YBC), and ultra-wide bandgap MgO (∼6.7 eV) as composite materials in this study. Compared to SDC and SDC/YBC electrolyte, the addition of MgO significantly broadens the depletion region and improves charge separation efficiency. Additionally, the ultra-wide bandgap of MgO minimizes electronic conductivity and prevents internal leakage. A fuel cell incorporating this composite electrolyte attained a peak power density of 826 mW cm −2 and an open-circuit voltage of 1.1 V at 550 °C. This represents a 12 % improvement over SDC/YBC electrolytes and a 47 % increase compared to SDC electrolytes. This study demonstrates that the SDC/YBC/MgO composite electrolyte effectively optimizes both ionic transport and interfacial stability.