A novel cobalt-free cathode material for proton-conducting solid oxide fuel cells

Developing a tailored cathode is of great importance for the improvement of proton-conducting solid oxide fuel cell (SOFC-H) performance. In this work, a novel cobalt-free cathode BaCe0.40Sm0.20Fe0.40O3-delta was designed for use in a SOFC-H. It was composed of homogeneously distributed BaCe1-x(Sm/Fe)(x)O3-delta and BaFe1-y(Sm/Ce)(y)O3-delta, which were synthesized by a simple in situ method, eliminating the separate synthesis and the mechanical mixing processes for the conventional composite materials. The BaCe0.40Sm0.20Fe0.40O3-delta cathode exhibited protonic, oxygen-ionic, and electronic conduction simultaneously in wet air, expanding the triple phase boundaries to the whole cathode. The symmetrical cell tests with BaCe0.40Sm0.20Fe0.40O3-delta as electrodes showed that the diffusion of O-ad(-) and reduction of O-TPB(-) were the rate limiting steps in wet air. The power density of the anode-supported single cell with Ni-BaCe0.80Sm0.20O3-delta (580 mu m) anode, BaCe0.80Sm0.20O3-delta (70 mu m) electrolyte and BaCe0.40Sm0.20Fe0.40O3-delta (53 mu m) cathode was 194.0, 169.2, and 137.1 mW cm(-2) at 750, 710, and 650 degrees C, respectively. These results are encouraging considering the cobalt-free nature and rather low electrical conductivity of the cathode material. The BaCe0.40Sm0.20Fe0.40O3-delta material demonstrated excellent catalytic activity towards the reactions on the cathode. Accordingly, the BaCe0.40Sm0.20Fe0.40O3-delta material can be a promising cathode for SOFC-H.