Engineering phase distribution in LSCF-CGO cathodes for enhanced electrochemical performance in SOFCs

Composite cathodes combining a mixed ionic–electronic conductor with an oxygen-ion conductor are key for intermediate-temperature solid oxide fuel cells (IT-SOFCs), as they increase the electrochemically active area and mitigate thermal expansion mismatch with the electrolyte. However, conventional fabrication methods, such as simple powder mixing, often yield inhomogeneous phase distributions and involve multiple processing steps that hinder scalability. In this work, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) - Ce 0.9 Gd 0.1 O 1.95 (CGO) composite cathodes are prepared by different routes, including conventional powder mixing, LSCF powders coated with CGO nanoparticles, CGO powders coated with LSCF nanoparticles and a co-synthetized nanocomposite obtained from a single precursor solution via the freeze-drying method. The electrodes are systematically characterized to correlate phase distribution and microstructure with electrochemical performance. The co-synthesized nanocomposite exhibits a significantly reduced particle size of 20 nm at 800 ºC, resulting in a polarization resistance of 0.08 Ω·cm 2 at 700 ºC, compared to 0.22 Ω·cm 2 for the powder-mixed electrode. Correspondingly, the power density of the cell employing the nanosized LSCF–CGO cathode increased by 37 % compared to the conventional electrode. These results demonstrate that freeze-drying provides a simple, scalable and effective synthesis route for high-performance LSCF–CGO nanocomposite cathodes, offering significant advantages over conventional preparation methods for IT-SOFC applications.