Highly active and durable double-doped bismuth oxide-based oxygen electrodes for reversible solid oxide cells at reduced temperatures

Abstract

Sluggish reaction kinetics on oxygen electrodes at reduced temperatures (<750 °C) remain a major challenge for the technical progress of reversible solid oxide cells (SOCs). To overcome this issue, the development of highly active and stable oxygen electrodes at intermediate temperatures (ITs, <750 °C) is urgent and essential. Rare earth-stabilized bismuth oxides are known to have high ionic conductivity and fast oxygen surface kinetics. Despite these advantageous properties, unlike conventional zirconia- or ceria-based materials, stabilized bismuth oxides have not been widely investigated as oxygen electrode components for reversible SOC applications. Herein, using the double doping strategy, we successfully developed Dy and Y co-doped Bi₂O₃ (DYSB), which showed record-high conductivity, ∼110 times higher than that of yttria-stabilized zirconia (YSZ) at ITs. This DYSB combined with conventional La_0.8Sr_0.2MnO_3−δ (LSM) significantly enhanced surface diffusion and incorporation of oxygen ion kinetics during the oxygen reduction reaction (ORR). Finally, the novel LSM-DYSB oxygen electrode was simply embedded in a YSZ electrolyte-based cell without a buffer layer. The LSM-DYSB SOC yielded an extremely high performance of 2.23 W cm⁻² in fuel cell mode as well as 1.32 A cm⁻² at 1.3 V in electrolysis mode at 700 °C, along with excellent long-term and reversible stabilities. This study demonstrates that the novel DYSB-based electrode has great potential as a high-performance oxygen electrode for next generation SOCs and provides new insight into rational design and material selection for solid state energy conversion and storage applications.