Behavior of La0.6sr 0.4Co0.2Fe0.2O3-δ Cathode Powders Surface Modified by Atomic Layer Deposition for Solid Oxide Fuel Cells

Atomic layer deposition (ALD) has been used to modify the surfaces of La0.6Sr0.4Co0.2Fe0.2O3-δ (LSCF) cathode powders with gadolinium doped ceria (GDC), zirconia, and cobalt doped zirconia (CDZ). Sintered porosities were ~41% for uncoated LSCF and 37-39% for surface modified powders. Mercury probe analysis showed similar pore size distributions. Symmetrical electrochemical cells showed marked improvements in polarization for the surface modified powders. GDC and CDZ coatings decreased polarization by up to 51 and 61%, respectively, at 800°C. Equivalent circuit modeling suggested little effect on gas diffusion through the porous structure, consistent with similar porosity values. Intermediate and high frequency contributions were significantly affected, suggesting a strong positive impact of the surface modification on both non-charge-transfer properties and charge-transfer properties. A pre-fabricated symmetrical cell treated with GDC via ALD showed very similar behavior to a symmetrical cell fabricated from surface modified GDC.