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

Abstract

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 BaCe_0.40Sm_0.20Fe_0.40O_3−δ was designed for use in a SOFC-H. It was composed of homogeneously distributed BaCe_1−x(Sm/Fe)_xO_3−δ and BaFe_1−y(Sm/Ce)_yO_3−δ, which were synthesized by a simple in situ method, eliminating the separate synthesis and the mechanical mixing processes for the conventional composite materials. The BaCe_0.40Sm_0.20Fe_0.40O_3−δ 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 BaCe_0.40Sm_0.20Fe_0.40O_3−δ 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–BaCe_0.80Sm_0.20O_3−δ (580 μm) anode, BaCe_0.80Sm_0.20O_3−δ (70 μm) electrolyte and BaCe_0.40Sm_0.20Fe_0.40O_3−δ (53 μm) cathode was 194.0, 169.2, and 137.1 mW cm⁻² at 750, 710, and 650 °C, respectively. These results are encouraging considering the cobalt-free nature and rather low electrical conductivity of the cathode material. The BaCe_0.40Sm_0.20Fe_0.40O_3−δ material demonstrated excellent catalytic activity towards the reactions on the cathode. Accordingly, the BaCe_0.40Sm_0.20Fe_0.40O_3−δ material can be a promising cathode for SOFC-H.