Low Area Specific Resistance La-Doped Bi₂O₃ Nanocomposite Thin Film Cathodes for Solid Oxide Fuel Cell Applications

In the context of solid oxide fuel cells (SOFCs), vertically aligned nanocomposite (VAN) thin films have emerged as a leading material type to overcome performance limitations in cathodes. Such VAN films combine conventional cathodes like LaSr_1-CoFe_1-O₃ (LSCF) and La_1-xSrMnO₃ (LSM) together with highly O^2- ionic conducting materials including yttria-stabilized zirconia (YSZ) or doped CeO₂. Next-generation SOFCs will benefit from the exceptionally high ionic conductivity (1 S cm^-1 at 730 °C) of Bi₂O₃-based materials. Therefore, an opportunity exists to develop Bi₂O₃-based VAN cathodes. Herein, we present the first growth and characterization of a Bi₂O₃-based VAN cathode, containing epitaxial La-doped Bi₂O₃ (LDBO) columns embedded in a LSM matrix. Our novel VANs exhibit low area specific resistance (ASR) (8.3 Ω cm² at 625 °C), representing ∼3 orders of magnitude reduction compared to planar LSM. Therefore, by demonstrating a high-performance Bi₂O₃-based cathode, this work provides an important foundation for future Bi₂O₃-based VAN SOFCs.