First principles study on the oxygen reduction reaction of the La1–xSrxMnO3–δ coated Ba1–xSrxCo1–yFeyO3–δ cathode for solid oxide fuel cells

A core-shell structured composite cathode for solid oxide fuel cell with Ba_1–xSr_xCo_1–yFe_yO_3–δ (BSCF) as core while La_1–xSr_xMnO_3–δ (LSM) as shell (LSM@BSCF) has been designed to achieve dual optimization of high stability and electrochemical activity. The atomic structure, oxygen vacancy formation, oxygen adsorption and diffusion, and CO₂ adsorption properties of the core-shell interface have been studied by the first principles method. The calculated binding energies and interface energies suggest that the combination of La/Sr–O plane of LSM (100) surface and the Co/Fe–O plane of BSCF (100) surface is the most favourable composite structure. The formation energy of oxygen vacancy in LSM is 1.73 eV, and 0.06 eV in BSCF, thus the oxygen vacancy is easier to be formed in BSCF, which results in better oxygen ion conductivity of BSCF than LSM. The oxygen diffusion barrier from LSM to BSCF at the interface is determined to be 0.66 eV, indicating an easy oxygen ionic transport between the interface. CO₂ is hard to be adsorbed onto the LSM@BSCF surface. Thus, the introducing of LSM Shell can prevent the BSCF cathode from being poisoned by CO₂.