Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

Intermediate temperature solid oxide fuel cells (IT-SOFCs) are cost-effective and efficient energy conversion systems. The sluggish oxygen reduction reaction (ORR) and the degradation of cathodes are critical challenges to the commercialization of IT-SOFCs. Here, a highly efficient multiphase (MP) catalyst coating, consisting of Ba_1−xCo_0.7Fe_0.2Nb_0.1O_3−δ (BCFN) and BaCO₃, to enhance the ORR activity and durability of the state-of-the-art lanthanum strontium cobalt ferrite (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ, LSCF) cathode is reported. The conformal MP catalyst-coated LSCF cathode shows a polarization resistance (R_p) of 0.048 Ω cm² at 650 °C, about one order of magnitude smaller than that of the bare LSCF. In an accelerated Cr-poisoning test, the degradation rate of the catalyst-coated LSCF electrode is 10⁻³ Ω cm² h⁻¹ (0.59% h⁻¹) over 200 h, only one fifth of the degradation rate of the bare LSCF electrode at 750 °C. In addition, anode-supported single cells with the MP catalyst-coated LSCF cathode show a dramatically enhanced peak power density (1.4 W cm⁻² vs 0.67 W cm⁻² at 750 °C) and increased durability against Cr and H₂O. Both experimental results and density functional theory-based calculations indicate that the BCFN phase improves the ORR activity while the BaCO₃ phase enhances the stability of the LSCF cathode.