B-site La, Ce, and Pr-doped Ba0.5Sr0.5Co0.7Fe0.3O3- perovskite cathodes for intermediate-temperature solid oxide fuel cells: Effectively promoted oxygen reduction activity and operating stability

Highly active cathode materials are crucial to accelerating the commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a facile doping strategy is proposed to promote the electrode performance of simple perovskite oxides by introducing the lanthanide (Ln = La, Ce, and Pr) ions into B-site. These materials are evaluated as promising cathodes for IT-SOFCs and characterized by electrochemical test between 500 and 700 °C. Among all Ba0.5Sr0.5Co0.7Fe0.28Ln0.02O3-δ perovskites, the Ba0.5Sr0.5Co0.7Fe0.28Pr0.02O3-δ (BSCFP) cathode exhibits the lowest polarization resistance (Rp) of 0.026 Ω cm2 at 700 °C, approximately 50% lower than that of the pristine Ba0.5Sr0.5Co0.7Fe0.3O3-δ (BSCF0.3). The BSCFP cathode-based fuel cell delivers a peak power density of 1083 mW cm−2 at 700 °C, along with exceptional operating stability for 150 h. Such performance may benefit from increased electrical conductivity and optimized surface oxygen process based on experiments and density-functional theory (DFT) calculations. The DFT calculations indicate that the Pr doping not only promotes the adsorption of oxygen species but also enhances the p-d hybridization of O 2p and Co/Fe/Pr 3d bands. The findings endow the performance modulation of the perovskite cathode systems involving the lanthanide doping at B-site.