Effects of neodymium doping on oxygen reduction activity in Pr2−xNdxNiO4+δ cathodes

Abstract

Single phase Pr2−xNdxNiO4+δ (x = 0, 0.3, 1, 1.7 and 2) (PNNO) compounds were synthetized by a sol-gel route. The thermal behavior of these compounds has been studied by Differential Thermal Analysis (DTA) and High Temperature X-ray Diffraction (HT-XRD). All PNNO solid solutions present an orthorhombic/tetragonal phase transition which does not affect the lattice volume. The calculated thermal expansion coefficients increase with Pr content but even at a high Pr content, the thermal expansion coefficients (TEC) values remain comparable with those of the solid state electrolytes. Electrochemical Impedance Spectroscopy (EIS) was carried out on symmetrical cells of porous PNNO electrodes on dense La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolytes. A chemical reactivity detected between PNNO and LSGM caused a decrease in the electrochemical performance of the PNNO cathodes. Even if this reactivity is avoided by using a buffer layer, the content of Pr does not improve the electrochemical performance of the PNNO cathodes.