Activity and Stability of (Pr 1-x Nd x ) 2 NiO 4 as Cathodes for Solid Oxide Fuel Cells

Abstract

This study is to complement an early article (Dogdibegovic et al., J. Electrochem. Soc., 163(13), F1344 (2016)) on the electrochem- ical activity and performance stability of (Pr1-xNdx)2NiO4+δ (PNNO) electrodes. Here, we report the crystal structure, electrical properties, and microstructures of PNNO series as the cathodes for solid oxide fuel cells. Rietveld refinements on powders (x = 0, 0.25, 0.50, 0.75, and 1) show that the unit cell volume decreases with an increase in x, primarily due to a decrease in the c lattice parameter. Larger cell volume (∼1.50%) and higher total electrical conduction (40%) in Pr2NiO4+δ are in favor with its mixed conducting properties during operation, but Pr2NiO4+δ cathode exhibits a severe phase evolution. Substitution of Pr with Nd shows the suppression of phase evolution in both thermally annealed powders and electrodes. An increase in Nd content leads to a full preservation of the parent phase in both (Pr0.25Nd0.75)2NiO4+δ and Nd2NiO4 after 2,500 hour annealing at elevated temperatures. ReactionwithGDCbuffer layerwas also suppressedwith the presence ofNd, whichwas shown by a reduction of Pr and Ni elemental diffusion into GDC bulk. STEM analysis confirms multiple phases present in an operated Pr2NiO4+δ electrode, while suppressed phase transition was observed in electrodes with high Nd content.