Smart utilization of cobaltite-based double perovskite cathodes on barrier-layer-free zirconia electrolyte of solid oxide fuel cells

Cobaltite-based double perovskite oxides with high electrocatalytic activity and conductivity have been developed as high-performance cathode alternatives for solid oxide fuel cells (SOFCs). However, the use of cobaltite-based double perovskites on Y₂O₃ stabilized ZrO₂ (YSZ)-based SOFCs requires the application of a doped ceria barrier layer. This is due to their poor chemical and physical compatibility with the YSZ electrolyte during high-temperature sintering and fabrication processes. Here we report a viable approach to in operando assemble double perovskites such as PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ (PBSCF), on YSZ electrolyte and thus effectively form an electrode/electrolyte interface without high-temperature processing. The electrochemical performance of the in situ assembled PBSCF cathode is comparable to that of the cathode prepared by conventional methods. A single cell with an in situ assembled PBSCF-GDC (Gd-doped ceria) cathode achieved a peak power density (PPD) of 1.37 W cm⁻² at 750 °C and exhibited a high stability at 500 mA cm⁻² and 750 °C for 100 h. Surface and cross-sectional microstructure analysis offer solid evidence that the PBSCF-GDC cathode/YSZ electrolyte interface was formed by electrochemical polarization. This work offers new opportunities to effectively and effortlessly use high-performance double perovskite cathodes in commercial SOFCs.