Exploration of the relationship between operation conditions and microstructure degradation of Ni/YSZ electrodes in solid oxide electrolysis cells

Abstract

Solid oxide electrolysis cells (SOEC) play an important role in the advancement of sustainable energy technologies, enabling efficient conversion of green electricity into chemical energy through electrolysis processes. However, the SOEC performance degradation mainly due to nickel migration in the Ni/yttria stabilized zirconia (YSZ) fuel electrode, poses a significant challenge to the widespread application and commercialization of the SOEC technology. In addition, the precise mechanisms behind the observed microstructural degradation are so far not fully understood and require further investigation. In this work, the microstructure evolution of Ni/YSZ electrodes after long-term operation in an H₂O/H₂ atmosphere at 800 °C is investigated using 2D SEM analysis and 3D reconstruction. The effect of variation in local current density and operation duration on Ni migration is explored. The inhomogeneity in the fuel electrode microstructure degradation along the gas flow direction is also examined. Furthermore, the influence of the fuel electrode overpotential and the operation duration on Ni migration is investigated based on the results from this work and previous research. Finally, a relationship between microstructural degradation and local and global operating conditions is proposed. The proposed correlation seems to fit the experimental data well. This makes it possible to predict the extent of Ni migration through operational conditions with more experimental verification in the future.