Highly accelerated oxygen reduction reaction kinetics in colloidal-processing-derived nanostructured lanthanum strontium cobalt ferrite/gadolinium-doped ceria composite cathode for intermediate-temperature solid oxide fuel cells

Abstract

Fully nanostructured La0.6Sr0.4Co0.2Fe0.8O3-δ/Gd0.2Ce0.8O1.9 [lanthanum strontium cobalt ferrite (LSCF)/gadolinium-doped ceria (GDC)] composite cathode is successfully demonstrated with conventional powder processing using nanocomposite particles, grown via a colloidal-processing-based bottom-up approach, as starting material. The cathode/electrolyte interface adheres well at a relatively low temperature of 900 °C because of the promoted surface diffusion of constituent elements by the higher surface energy of the nano-sized particles. By contrast, successful fabrication of a nanostructured porous cathode composed of uniformly distributing LSCF and GDC grains with a diameter of 50–70 nm strongly supports the prevented grain growth and pore closure by the co-existing hetero-phases in the composite particles acting as bulk diffusion barrier of each other's constituents during sintering. The nanocomposite cathode exhibits quite low area-specific polarization resistances for oxygen reduction reaction (ORR) of 0.127, 0.054, 0.032, 0.015 and 0.009 Ω cm2 at 600, 650, 700, 750 and 800 °C, respectively. These are significantly lower than those reported in the literature. The highly accelerated ORR kinetics contribute directly to the very high power densities of the anode-supported cells of 0.40, 0.77, 1.40, 2.32, and 3.29 W cm−2 at 600, 650, 700, 750, and 800 °C, respectively, with a cell voltage at 0.7 V.