PNNL

Abstract

This study explored the decomposition mechanism of a La2NiO4 phase in the La2NiO4-La0.5Ce0.5O2-? (LNO-LDC) oxygen electrode in a solid oxide electrolysis cell after testing at 800°C. Scanning electron microscopy and scanning transmission electron microscopy examinations of the LNO-LDC oxygen electrode before and after testing were undertaken. Other than P contamination in the form of lanthanum phosphate grains and P-rich deposits along all grain boundaries, LNO and LDC phases were intact without degradation in the as-fabricated electrode. However, mild to aggressive phase decomposition in LNO was observed after testing at 800°C for 900 h. The evolution of the LNO phase decomposition was noted beginning with the exsolution of Ni into the surrounding LNO matrix and grain boundaries, forming La-rich and Ni-rich phases in the LNO correspondingly. This study will illustrate a detailed decomposition progress of the LNO phase at the atomic level under a solid oxide electrolysis cell operation condition.