Oxygen transport properties of La2Ni1−xCuxO4+δ mixed conducting oxides

Materials formulated La2Ni1−xCuxO4+δ (0⩽x⩽1) have been prepared and characterized using various techniques: a particular attention has been paid to their mixed conduction properties in view of application as SOFC cathode. These oxides show a good thermal stability in terms of oxygen over-stoichiometry and thermal expansion coefficient (TEC ≈13×10−6 K−1). In addition, they exhibit high electrical conductivity (≈100 S·cm−1) as well as high values of oxygen diffusion and surface exchange coefficients (D∗ and k) which have been determined using secondary ion mass spectroscopy (SIMS) of the 18O isotope. Highly dense ceramics have been prepared for these measurements, which has required a specific study of the densification of these materials. They exhibit D∗ and k coefficients one order of magnitude higher than those of the best perovskite materials. The pure nickelate seems to show the most promising properties for the oxygen reduction electrocatalysis.