Nd2 − xLaxNiO4 + δ, a mixed ionic/electronic conductor with interstitial oxygen, as a cathode material

The performance of Nd2 − xLaxNiO4 + δ as a cathode material for solid oxide fuel cell (SOFC) was evaluated in this paper. Substitution of smaller Nd3+ ion for La3+ in La2NiO4 + δ increased the retention of mobile interstitial oxygen defects (Oi″ ions). The concentration of the Oi″ ions in Nd2NiO4 + δ was stabilized at δ ≈ 0.12 at 800 °C in air after thermal cycling. As a mixed oxide-ion/electronic conductor (MIEC), Nd2NiO4 + δ gave a performance comparable to that of the best perovskite cathode material, SrCo0.8Fe0.2O3 − δ (SCF), for the Sm-doped ceria (SDC) electrolyte-supported SOFC. However, the Nd2NiO4 + δ cathode exhibited a higher overpotential with La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) as the electrolyte, presumably due to the interdiffusion of La3+ and Nd3+ ions across the electrolyte/cathode interface and subsequent formation of ion-blocking phases at the interface. La1.2Nd0.8NiO4 + δ, on the other hand, provided La isoactivity across the LSGM/cathode interface and therefore an improved performance with the LSGM electrolyte. Since Nd2 − xLaxNiO4 + δ contains neither Sr nor Co, as a cathode, it might be compatible with the electrolytes such as yttria-stabilized zirconia without the need of a buffer layer.