Nd1.8Sr0.2NiO4−δ:Ce0.9Gd0.1O2−δ composite cathode for intermediate temperature solid oxide fuel cells

The (100 − x)Nd1.8Sr0.2NiO4−δ:(x)Ce0.9Gd0.1O2−δ (x = 00, 10, 20, 30, 40 and 50 vol%) composites are obtained by ball milling requisite mixture at 200 rotations per minute for 2 h under acetone followed by sintering at 1000 °C for 4 h. The increase in concentration of Ce0.9Gd0.1O2−δ in composite reduces the crystallite size of host Nd1.8Sr0.2NiO4−δ from 378 ± 0.7 to 210 ± 0.8 nm. The dc (electronic) conductivity of composite decreases moderately with an increase in Ce0.9Gd0.1O2−δ content in composite up to 30 vol%, and it decreases abruptly, thereafter at x > 30. A minimum polarization resistance value of 0.24 Ω cm2 (at 700 °C) is obtained for a (70)Nd1.8Sr0.2NiO4−δ:(30)Ce0.9Gd0.1O2−δ composite cathode, and this value is attributed to the optimal dispersion of Ce0.9Gd0.1O2−δ into Nd1.8Sr0.2CuO4−δ matrix. The oxygen partial pressure dependent polarization resistance study suggests that the charge transfer and the non-charge transfer oxygen adsorption–desorption along with diffusion are the major rate limiting steps of overall oxygen reduction reaction process.