Interfacial Active Layers for Redox-Stable Symmetrical Solid Oxide Fuel Cells

The incorporation of active layers has become an effective strategy to reduce interfacial polarization losses in solid oxide fuel cells (SOFCs). However, the development of redox-stable active layers capable of operating under both oxidizing and reducing atmospheres in symmetrical cell configurations remains challenging. In this work, we develop a redox-stable Sr 0.98 Fe 0.75 Ti 0.25 O 3-δ -Ce 0.9 Gd 0.1 O 1.95 (SFT-CGO) nanocomposite that maintains its structural and chemical integrity during cycling between air and hydrogen atmospheres. When deposited via spray-pyrolysis as a nanostructured active layer, the composite forms a dense and homogeneous interface with the electrolyte, facilitating charge transfer and oxide-ion transport while increasing the density of electrochemically active surface pathways. This optimized interface significantly reduces the polarization resistance under both anodic and cathodic operation. As a result, a symmetrical electrolyte-supported cell incorporating the active layer delivers a peak power density of 630 mW cm -2 at 800 °C, compared to 380 mW cm -2 for the reference cell without the active layer. These results demonstrate that a redox-stable nanocomposite interlayer offers a scalable approach to improving interfacial properties and overall performance in symmetrical solid oxide cells.