Temperature-controlled in-situ construction of composition-tunable nanoparticle-decorated SOFC cathodes with enhanced oxygen reduction kinetics and CO2 tolerance

High oxygen reduction reaction (ORR) catalytic activity and CO₂ resistance of the cathode are fundamental to the commercial application of solid oxide fuel cells (SOFCs). Therefore, we develop a temperature-driven reduction-reoxidation strategy to in-situ construct heterostructured perovskite cathodes decorated with different nanoparticles by controlling the reduction temperature. For (Pr_0.4Sr_0.6)_0.95Co_0.2Fe_0.8-xNi_xO_3-δ (PSCFN, x = 0.05, 0.1), reduction (@700 °C)-reoxidation results in the exsolution of a Co_mFe_nNi_3-m-nO₄ spinel phase on the perovskite scaffold surface, while reduction (@750 °C)-reoxidation leads to the formation of both Co_mFe_nNi_3-m-nO₄ spinel phase and NiO nanoparticles. The exsolution of these highly active species increases the quantity of oxygen reduction active sites and effectively suppresses Sr segregation. The simultaneous formation of Co_mFe_nNi_3-m-nO₄ spinel phase and NiO nanoparticles induces B-site ion vacancies in the main phase, therefore facilitates the formation of oxygen vacancies. Additionally, the presence of Co_mFe_nNi_3-m-nO₄/NiO/PSCFN heterointerfaces promotes oxygen adsorption and transfer. The strong interactions among Co_mFe_nNi_3-m-nO₄, NiO, and PSCFN significantly enhance the structural stability. At 800 °C, Reo2-PSCFN0.1 achieves an output performance of 1.12 W cm⁻², representing a 36.6 % enhancement compared to PSCFN0.1. Moreover, the Rp of Reo2-PSCFN0.1 is merely 0.0186 Ω cm², marking a 40.4 % decrease relative to PSCFN0.1. This temperature-driven reduction-reoxidation strategy shows great promise as a novel approach for creating high-performance IT-SOFC cathodes.