Unveiling the high-temperature degradation mechanism of solid oxide electrolysis cells through direct imaging of nanoscale interfacial phenomena

Solid oxide electrolysis cell (SOEC) technology potentially offers the most efficient means of clean H2 production. Currently, the most critical issue is the delamination of the air electrode, but its fundamental cause has long been elusive. Using cutting-edge transmission electron microscopy techniques and density functional theory calculations, we reveal nanometer-scale interfacial degradation phenomena occurring in the early stages, clarifying the entire process of delamination and the origin thereof. During SOEC operation, oxygen ions accumulate at specific locations where they cannot be released as a gas. The annihilation of oxygen vacancies modifies the unit cell structure, causing anisotropic lattice strain; further injection of excess oxygen ions creates dislocations and segmented subgrains. Subsequently, these ions initiate the formation of nanopores, which eventually develop into cracks and delaminate the electrode. These previously undiscovered structural alterations contradict the long-held but unsubstantiated notion of gas pressure build-up, providing novel guidance for future development. Advanced transmission electron microscopy analysis uncovers the fundamental mechanisms behind nanometer-scale interfacial degradation phenomena in high-temperature solid oxide electrolysis cells.