Low Area Specific Resistance La-Doped Bi<sub>2</sub>O<sub>3</sub> Nanocomposite Thin Film Cathodes for Solid Oxide Fuel\nCell Applications

In the context of\nsolid oxide fuel cells (SOFCs), vertically aligned\nnanocomposite (VAN) thin films have emerged as a leading material\ntype to overcome performance limitations in cathodes. Such VAN films\ncombine conventional cathodes like La<sub><i>x</i></sub>Sr<sub>1–<i>x</i></sub>Co<sub><i>y</i></sub>Fe<sub>1–<i>y</i></sub>O<sub>3</sub> (LSCF)\nand La<sub>1–x</sub>Sr<sub><i>x</i></sub>MnO<sub>3</sub> (LSM) together with highly O<sup>2–</sup> ionic conducting\nmaterials including yttria-stabilized zirconia (YSZ) or doped CeO<sub>2</sub>. Next-generation SOFCs will benefit from the exceptionally\nhigh ionic conductivity (1 S cm<sup>–1</sup> at 730 °C)\nof Bi<sub>2</sub>O<sub>3</sub>-based materials. Therefore, an opportunity\nexists to develop Bi<sub>2</sub>O<sub>3</sub>-based VAN cathodes.\nHerein, we present the first growth and characterization of a Bi<sub>2</sub>O<sub>3</sub>-based VAN cathode, containing epitaxial La-doped\nBi<sub>2</sub>O<sub>3</sub> (LDBO) columns embedded in a LSM matrix.\nOur novel VANs exhibit low area specific resistance (ASR) (8.3 Ω\ncm<sup>2</sup> at 625 °C), representing ∼3 orders of magnitude\nreduction compared to planar LSM. Therefore, by demonstrating a high-performance\nBi<sub>2</sub>O<sub>3</sub>-based cathode, this work provides an important\nfoundation for future Bi<sub>2</sub>O<sub>3</sub>-based VAN SOFCs.