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

Abstract

Although carbon-free hydrogen production by water electrolysis represents an ideal approach to achieve net-zero emissions, the associated cost is substantially higher than that of conventional fossil fuel-based processes. Among various electrolyzer types, the solid oxide electrolysis cell (SOEC), which operates at high temperatures typically in excess of 700°C, offers the strongest potential for cost reduction owing to its unrivaled efficiency. Currently, the major challenge hindering its commercialization is rapid performance degradation, particularly owing to the delamination of the air electrode. Although significant research efforts have been devoted to understanding the fundamental cause of this degradation, they have been unsuccessful owing to the difficulty of characterizing nanoscale interfacial phenomena. In this study, we adopted novel analytical techniques including precession electron diffraction in transmission electron microscopy to elucidate the origin and evolution of interfacial degradation. Specifically, we visualized the entire delamination process involving the local accumulation of oxygen ions, change in anisotropic lattice strain, generation of dislocation and subgrain boundaries, and formation of aligned nanopores. The resulting comprehensive understanding of SOEC degradation phenomena establishes a basis for rational development strategies, and the associated detailed knowledge of atomic/nanoscale interfacial phenomena represent a valuable asset for the entire energy community.