Power density vs ionic radii correlations in REBa2Cu3O6+ẟ (RE = La, Nd, Sm, Gd and Y) IT – SOFC potential cathodes

Abstract

Co-free REBa2Cu3O6+ẟ (RE= La, Nd, Sm, Gd and Y) triple perovskite ceramics prepared by auto-combustion were systematically studied as cathodes for intermediate-temperature solid oxide fuel cells. The orthorhombic to tetragonal phase transition typical of these compounds was studied, and its relation with electrochemical performance due to oxygen vacancy ordering variations was assessed as neutral. The model that best fits the electrochemical impedance spectroscopy data obtained for symmetrical cells prepared on 10% gadolinia-doped ceria (GDC, Gd0.1Ce0.9O1.95) electrolyte pellets indicates an oxygen diffusion/incorporation co–limited process is the rate-limiting step of the oxygen reduction reaction (ORR). A maximum power density of 425 mW.cm−2 was obtained for the YBa2Cu3O6+ẟ material deposited by screen-printing on a commercial half-cell with 8YSZ-Ni anode and 8YSZ electrolyte coated with a GDC barrier layer. A clear correlation is observed between the power density and ionic radii of the RE cation of these triple perovskites.