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

Simulations utilizing molecular dynamics (MD) were applied to study the anisotropic diffusion in the a-b plane of double perovskite structure, GdBaCo2O5.5 (GBCO(5.5)). Diffusion coefficient of GBCO(5.5) was calculated to be 5 x 10(-8) cm(2) 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+delta. In the co-doped structure, increasing diffusion was observed on increasing the Fe doping to x = 1 (D = 7.5 x 10(-8) cm(2) s(-1) at 923 K). This was contrary to the Pr or Nd based co-doped materials, LnBa(1-y)Sr(y)Co(2-x)Fe(x)O(5+delta) (Ln = Pr, Nd), where maximum diffusion was calculated for Fe doping level at x = 0.5 (D = 5.16 x 10(-8) cm(2) s(-1) for Ln = Pr and D = 1.18 x 10(-7) cm(2) 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. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.