Three-dimensional structural analyses of the oxygen electrodes in solid oxide electrolysis cells

Solid oxide electrolysis cells (SOECs) have garnered interest as efficient devices for production of clean fuel such as hydrogen gas. However, the industrialization of SOEC technology has encountered significant challenges, such as unsatisfactory performance and insufficient durability. In this study, we aimed to improve the electrochemical performance and stability of the SOEC air electrode by modifying it at various annealing temperatures (900, 1000, and 1100 degrees C). Electrochemical testing revealed that the SOEC cell with the electrode annealed at 1000 degrees C for 1 h exhibited the highest current density of 0.88 A/cm2 at 750 degrees C and 1.3 V, which is 1.76-times higher than that of the cell with the unoptimized electrode annealed at 900 degrees C. Three-dimensional microstructural analyses using Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) confirmed that the optimized cell is the most porous with sufficient pore surface area, thereby facilitating electrochemical reactions and gas transport, and preventing delamination of the air electrode resulting from lower oxygen partial pressure difference between the barrier layer and air/electrode interface. Side reactions at the interface, including the generation of resistant SrZrO3, are concurrently avoided. These findings demonstrate the potential of the modified SOEC air electrode for improving electrochemical performance and stability.