Enhancing Oxygen Reduction Activity and Structural Stability of La_0.6Sr_0.4FeO_3−δ by 1 mol % Pt and Ru B-Site Doping for Application in All-Perovskite IT-SOFCs

The choice of suitable electrodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) represents a challenge toward full commercialization. Conventional materials used for high-temperature SOFCs, such as Ni-containing anodic cermets (Ni-YSZ) and Co-based perovskite cathodes (La0.6Sr0.4Fe0.8Co0.2O3−δ, LSCF, Ba0.6Sr0.4Fe0.8Co0.2O3−δ, BSCF), suffer from compatibility issues if coupled with a highly performing La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte. Thus, perovskite-type mixed conductors have been extensively studied as potential electrodes for all-perovskite devices. In the present study, the effect of controlled noble metal doping at the B-site of La0.6Sr0.4FeO3−δ (LSF) is investigated. The introduction of 1 mol % ruthenium or platinum is successfully achieved: La0.6Sr0.4Fe0.99Ru0.01O3−δ (LSFR) and La0.6Sr0.4Fe0.99Pt0.01O3−δ (LSFP) single-phase compounds are obtained. The structural, morphological, electrical, and electrochemical characterizations of LSFR and LSFP are provided and discussed. Both platinum and ruthenium doping reveal to be effective in improving the electrocatalytic properties of the parent perovskite structure: Pt increases the number of oxygen vacancies, thus promoting the oxygen reduction reaction (ORR) and reducing the LSF polarization resistance by 12.9%, while Ru improves LSF stability in reducing conditions promoting the exsolution of metal nanoparticles. All-perovskite cells LSFR/LSGM/LSFP are fabricated and tested in H2, showing remarkable performances in the intermediate-temperature range.