Electrode Properties of the Ruddlesden–Popper Series, La n ₊₁ Ni n O 3 n +1 ( n =1, 2, and 3), as Intermediate‐Temperature Solid Oxide Fuel Cells

The Ruddlesden–Popper phases, La n +1 Ni n O 3 n +1 ( n =1, 2, and 3), were synthesized by a solid‐state reaction for use as cathodes in an intermediate‐temperature (500°–700°C) solid oxide fuel cell. The samples crystallized into an orthorhombic layered perovskite structure. The overall electrical conductivity increased with the increase of n in the intermediate temperature range. Single test‐cells, which consisted of samarium‐oxide‐doped ceria (SDC; Sm 0.2 Ce 0.8 O x ) as an electrolyte, Ni–SDC cermet (Ni–SDC) as an anode, and La n +1 Ni n O 3 n +1 as a cathode, were fabricated for measurements of cell performance at 500°–700°C. Current interruption measurements revealed that both the ohmic and overpotential losses at 700°C decreased with the increase of n . La 4 Ni 3 O 10 was found to exhibit the best cathode characteristics in the La n +1 Ni n O 3 n +1 series. Maximum test‐cell power densities with La 4 Ni 3 O 10 ( n =3) were 10.2, 36.5, and 88.2 mW/cm 2 at 500°, 600°, and 700°C, respectively.