Oxygen anion diffusion in double perovskite GdBaCo2O5+δ and LnBa0.5Sr0.5Co2−xFexO5+δ (Ln = Gd, Pr, Nd) electrodes

•Oxygen anion diffusion in double perovskite was calculated using molecular dynamics simulations.•Diffusion increases on increasing the doping level of Iron in GBSCFO.•Maximum diffusion for GBSCFO was calculated for 50% Fe doping.•In PBSCFO and NBSCFO an optimum diffusivity was obtained for 25% Fe doping.•The trends of diffusivity correlates well to the electrochemical performance.

Simulations utilizing molecular dynamics (MD) were applied to study the anisotropic diffusion in the a–b plane of double perovskite structure, GdBaCo2O5.5 (GBCO5.5). Diffusion coefficient of GBCO5.5 was calculated to be 5 × 10−8 cm2 s−1 at 873 K. The calculated diffusion coefficient was observed to increase on increasing temperature with an activation energy of 50.8 kJ/mol. Similar MD simulations were employed to study the effect of the level of Fe doping at the B-site of the co-doped GdBa0.5Sr0.5Co2−xFexO5+δ. In the co-doped structure, increasing diffusion was observed on increasing the Fe doping to x = 1 (D = 7.5 × 10−8 cm2 s−1 at 923 K). This was contrary to the Pr or Nd based co-doped materials, LnBa1−ySryCo2−xFexO5+δ (Ln = Pr, Nd), where maximum diffusion was calculated for Fe doping level at x = 0.5 (D = 5.16 × 10−8 cm2 s−1 for Ln = Pr and D = 1.18 × 10−7 cm2 s−1 for Ln = Nd at 873 K). The trend in diffusivity correlates well with the trends in the measured peak power density of a solid oxide fuel cell fabricated with these electrode materials.