Effect of the cobalt content on properties of La2Ni1-xCoxO4+δ

Ruddlesden-Popper-type La2NiO4+δ oxide is considered as a potential cathode for solid oxide fuel cell applications. In this work, the tailoring possibility of the cathode material properties by doping with a small amount of Co has been investigated. The initial powders were synthesized by the self-propagating high-temperature synthesis method. The sintering kinetics, thermal expansion, electrical conductivity, catalytic activity of La2Ni1-xCoxO4+δ (0 ≤ x ≤ 0.3) as well as their interaction with Zr0.84Y0.16O2-δ (YSZ) and Ce0.73Gd0.27O2-δ (GDC) electrolytes have been studied. It was shown that the coefficient of thermal expansion of the investigated compositions increases with increasing the Co content. The Co doping leads to decreasing of La2Ni1-xCoxO4+δ conductivity in the temperature range below 600°С, whereas at higher temperatures, compositions with x = 0.2 and 0.3 have higher conductivity than La2NiO4. The polarization resistance of the cathodes in contact with YSZ increases with increasing the Co content. However, in contact with GDC the La2Ni0.8Co0.2O4+δ composition has the lowest polarization resistance of 0.4 Ω cm2 (at 800 °C), which is 1.5 times less than that of La2NiO4+δ. Therefore, it was concluded that doping with the appropriate amount of Co could further improve the properties of lanthanum nickelate cathode. •CTE of La2Ni1-xCoxO4 increases with increasing Co content.•Below 600 °C the conductivity of La2Ni1-xCoxO4 decreases with increasing Co content.•Above 600°С the La2Ni1-xCoxO4 at x = 0.2, 0.3 have higher conductivity than La2NiO4.•The polarization resistance of La2Ni1-xCoxO4 – YSZ increases with increasing Co.•The lowest polarization resistance of La2Ni1-xCoxO4 – GDC is observed at x = 0.2.