High performance zirconia-bismuth oxide nanocomposite electrolytes for lower temperature solid oxide fuel cells

• A novel nanostructured ESB-YSZ composite electrolyte is developed.
• The nanocomposite electrolyte is sintered as low as 800 °C.
• ESB-YSZ exhibits 5 times higher ionic conductivity than that of YSZ.
• The high ionic conductivity is maintained for ∼600 h, demonstrating high stability.
• Oxygen reduction reaction with ESB-YSZ is effectively enhanced by ∼70% compared to YSZ.

We develop a novel nanocomposite electrolyte, consisting of yttria-stabilized zirconia (YSZ) and erbia-stabilized bismuth oxide (ESB). The 20 mol% ESB-incorporated YSZ composite (20ESB-YSZ) achieves the high density (>97%) at the low sintering temperature of 800 °C. The microstructural analysis of 20ESB-YSZ reveals the characteristic nanocomposite structure of the highly percolated ESB phase at the YSZ grain boundaries (a few ∼ nm thick). The ionic conductivity of 20ESB-YSZ is increased by 5 times compared to that of the conventional YSZ due to the fast oxygen ion transport along the ESB phase. Moreover, this high conductivity is maintained up to 580 h, indicating high stability of the ESB-YSZ nanocomposite. In addition, the oxygen reduction reaction at the composite electrolyte/cathode interface is effectively enhanced (∼70%) at the temperature below 650 °C, mainly due to the fast dissociative oxygen adsorption on the ESB surface as well as the rapid oxygen ion incorporation into the ESB lattice. Thus, we believe this ESB-YSZ nanocomposite is a promising electrolyte for high performance solid oxide fuel cells at reduced temperatures.

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