Stability and Activity of (Pr1-xNdx)2NiO4 as Cathodes for Solid Oxide Fuel Cells: I. Quantification of Phase Evolution in Pr2NiO4

Praseodymium nickelate (Pr2NiO4) is an active oxygen electrode for solid oxide fuel cells, but undergoes phase transition at elevated temperatures (e.g., 750 degrees C). Quantification of this phase evolution in an operating single cell is challenging because of the overlap of X-ray diffraction (XRD) peaks between the cathode and oxide current collector. In this work, we replace the oxide current collector with a gold metal grid, circumventing these challenges by allowing the exposure of the cathode to the X-ray beam, while eliminating peak overlap. Quantification of the phase evolution was performed by a least-squares fitting of the linear combination of XRD standards against the experimental patterns. Energy-dispersive spectroscopy analysis on long-term operated cells showed the absence of reactions between the gold grids and the cathodes. Additionally, the grids exhibited excellent mechanical stability under operating conditions and enabled similar cell performance as an oxide current collector.