Surface modification of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ cathode by infiltrating A-site deficient non-strontium La_0.94Ni_0.6Fe_0.4O₃ perovskite for solid oxide fuel cells

La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) is a promising cathode for intermediate temperature range, however strontium tends to segregate on the surface of the cathode and reacts with CO₂ from atmosphere and Cr from interconnect, which deteriorates its oxygen reduction reaction (ORR) activity. Here, we propose infiltrating stable and active A-site deficient Fe-doped lanthanum nickelate perovskite La_1-xNi_yFe_1-yO₃ without Sr element over the LSCF by delicately tailoring the infiltrating amount. It is found that 150 μL La_0.94Ni_0.6Fe_0.4O₃(LNF94) infiltrated LSCF (LNF94@LSCF) composite cathode with improved ORR catalytic activity, its symmetrical cell area specific resistance is 0.041 Ω·cm² and its single cell exhibited 1.08 W cm^-2 output power density at 800 ℃. The heterogeneous interface significantly improved the electron conduction and enhanced the dissociation of oxygen molecules which has been verified by the energy band alignment of LSCF and LNF94. Moreover, the core-shell LNF94@LSCF composite cathode showed excellent long-term tolerance to CO₂ and Cr atmosphere.