The relative role of oxygen surface reaction and bulk transport in double perovskites materials of series LnBa1-xSrxCoyFe1-yO5+δ (Ln=Gd, Pr) was studied by performing experiments and theoretical Density Functional Theory (DFT) and Molecular Dynamic (MD) simulations. The diffusivity in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) was calculated to be higher by an order of magnitude as compared to PrBaCO2O5+δ (Figure 1a), correlating with the reported electrochemical performance. Dense 2 µm thick thin-film electrodes of PBSCF were fabricated in a geometrically well-defined manner on Gd0.2Ce0.8O2–δ (GDC) electrolyte by utilizing a spray pyrolysis method. The measured polarization resistance (7.21 cm2 /sec at 873 K) of the electrode (Figure 1b) was ascribed to the bulk diffusion. The oxygen vacancy formation in the Gd-plane (Eov = 98.5 kJ/mol) of GdBaCo2O5+δ (GBCO) was measured to be lower than that of Ba-plane (Eov =266.3 kJ/mol), therefore, vacancies were concentrated in the Gd-plane as compare to other planes. Surface energy of the Ba-plane was measured to be minimum (Υ =7.3 kJ/mol), which makes it most abundunt surface. Therefore, larger size bulk microstructures of GBCO having Ba-plane as a most exposed surface and gives lesser oxygen anion diffusivity (D =6.04 x10-10 cm2 /sec). GBCO particles of reduced size are expected to expose higher energetic Gd-plane, which may enhance diffusivity. A novel bio-milling synthesis method was developed to synthesized particles of size &lt; 20 nm, in which chemically synthesized GBCO was subjected to a fungus Saccharomyces Cerevisiae, for 72 hr of fermentation. Approximately 20% improvement in the area specific resistance of bio-milled fabricated electrode is observed, shown in Figure 1c.

Unraveling oxygen anion transport in nanostructured double perovskite electrodes for solid oxide fuel cells

254th National Meeting (2017)

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