In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes

Abstract

The phase stability and compatibility of intermediate temperature solid oxide fuel cell (IT-SOFC) composite cathodes of lanthanum nickelate, La₂NiO_4+δ (LNO), and ceria-gadolinium oxide, Ce_0.9Gd_0.1O_2−δ (CGO10), have been investigated by high resolution synchrotron X-ray diffraction (XRD). No reaction was observed between LNO and CGO10 at temperatures of up to 900 °C when the composite is open to an ambient air environment. However, in a sealed capillary environment the 50 : 50 wt% LNO:CGO10 composite undergoes a partially reversible reaction at temperatures of 750 °C and above, whereby LNO decomposes to La₂O₃ and Ni. Changes in the CGO10 Bragg peaks indicate that this component is actively involved in this process. This study shows that the phase stability of LNO:CGO10 composites is highly dependent on oxygen partial pressure. In addition, it is observed that ex-situXRD is insufficient to determine the presence of reactivity in composite cathodes and that high resolution in situXRD measurements are required to obtain details of the complexity of phase stability in SOFC composite cathodes.