Advanced electrocatalytic performance of the configuration entropy cobalt-free Bi0.5Sr0.5FeO3–δ cathode catalysts for solid oxide fuel cells

The medium-entropy perovskite oxide Bi_0.5Sr_0.5Fe_0.85Nb_0.05Ta_0.05Sb_0.05O_3–δ (BSFNTS) is evaluated as a potential cathode catalyst for solid oxide fuel cells (SOFCs). The crystal structure, electrocatalytic activity, oxygen reduction kinetics, and CO₂ tolerance are systematically investigated. At 700 °C, the BSFNTS cathode exhibits excellent electrochemical performance with a polarization resistance as low as 0.095 Ω cm². The maximal power density of the fuel cell with the BSFNTS cathode is 900 mW cm⁻². Furthermore, the rate control step for the oxygen reduction reaction (ORR) of the electrode is primarily identified as the adsorbed and diffusion process of the molecule oxygen. The BSFNTS electrode presents excellent CO₂ tolerance and durability in a CO₂-containing atmosphere, which is related to the high acidity of Bi, Nb, Ta, and Sb cations and the larger average bonding energy of BSFNTS. The preliminary results indicate that BSFNTS medium-entropy oxide is an attractive cathode electrocatalyst for SOFCs.