Addressing the origin of highly catalytic activity of A-site Sr-doped perovskite cathodes for intermediate-temperature solid oxide fuel cells

Highly active cathode materials are crucial to accelerating the commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, Sr-doped Pr0.94Ba1-xSrxCo2O5+delta (PBSxCO) perovskite oxides are evaluated by experimental and theoretical studies. The phase transformation from tetragonal layered double perovskite to cubic simple perovskite can be identified with increasing the Sr fraction. Benefiting from enhanced electrical conductivity and oxygen surface rate, the PBSxCO catalysts deliver excellent electrochemical performance, as evidenced by symmetrical and completed cells test. Among all compositions, the Pr0.94Ba0.7Sr0.3Co2O5+delta (PBS0.3C0) cathode has the lowest polarization resistance (R-p) of 0.031 Omega cm(2) at 700 degrees C. The PBS0.3C0 cathode-based fuel cell produces a peak power density of 1077 mW cm(-2), along with a steady operating for 130 h at 700 degrees C. From the density functional theoretical (DFT) calculations, it is discovered that stronger Co 3d-O 2p hybridization is recognized in the Sr substituting model compared with undoped one. Furthermore, the decreased free energy for oxygen adsorption may facilitate the oxygen reduction reaction (ORR) kinetics. These findings highlight the origin of optimal ORR activity induced by A-site alkaline earth doping in the perovskite catalysts, endowing the rational design of oxide catalysts.

Automated summary

In this study, Sr-doped PBSxCO perovskite oxides were evaluated as cathode materials for IT-SOFCs through experimental and theoretical studies. It was found that increasing Sr fraction led to a phase transformation in the perovskite structure, resulting in improved electrochemical performance of the cathode. These findings are of significance for the rational design of oxide catalysts.