Insights into strontium zirconate-induced interface pressures in solid oxide electrolysis cells

Abstract

Modeling the oxygen partial pressure at the interfaces of solid oxide electrolysis cells is essential to understand their degradation. Here we present a bilayer electrolyte equivalent circuit model that does not assume continuity of the oxygen chemical potential at the electrolyte interface, in line with experimental results. We use the model to assess the assumption that strontium zirconate growth is responsible for oxygen electrode interface pressure increases and delamination. We find that 5% Y-doped strontium zirconate does not drive fracture for accumulations up to 250 nm except at 800°C and 1.6V. With a low electronic conductivity, 5% La-doped strontium zirconate shows a region of stability where increased thickness actually stabilizes the interface pressure. We also highlight the importance of modeling interface stability with the proper electronic conductivity. Finally, we present interface stability requirements and contextualize the strontium zirconate composition results in terms of interface stabilization strategies.