Nickel-substituted Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ: a highly active perovskite oxygen electrode for reduced-temperature solid oxide fuel cells

A key need for the advancement of high-performance solid oxide fuel cells (SOFCs) is to develop viable cathode materials with high electrocatalytic activity for the oxygen reduction reaction (ORR) at reduced operating temperatures below 700 °C. Here, we report a Ni-substituted perovskite composition Ba_0.5Sr_0.5Co_0.7Fe_0.2Ni_0.1O_3-δ (BSCFN) as a potential cathode material focusing on enhancing the electrochemical performance. Considerable attention is paid to the research of physicochemical properties primarily by crystal structure and oxygen transport measurements, with the aim to build up the correlation with the ORR activity. With the BSCFN cathode, a symmetrical cell achieves a very low area-specific polarization resistance of only ∼0.018 Ω cm² and a single cell delivers a maximum power density as high as ∼1.8 W cm^-2 at 650 °C. Such a large electrode performance improvement is attributed to the sustained cubic-symmetry perovskite structure and fast oxygen kinetics promoted by Ni substitution. The desirable ORR activity and durability highlight the potential of BSCFN as a highly promising oxygen electrode for reduced-temperature SOFCs.