Heterointerfacial engineered NdBaCo2O5+δ/BaCo0.8Ta0.2O3−δ composite cathodes with mitigated thermal expansion and accelerated ORR kinetics for IT-SOFCs

Improving the oxygen reduction reduction activity and thermal stability of cathode materials is critical to advancing the commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, a high-performance mixed ionic-electronic conductor (MIEC) BaCo 0.8 Ta 0.2 O 3-δ phase is incorporated into the lattice of NdBaCo 2 O 5+δ (NBC) double perovskite. Such composite construction elevates the oxygen vacancy concentration, lowers the thermal expansion coefficient (TEC) of NBC-based materials, and simultaneously improves electrocatalytic activity and long-term operational durability of IT-SOFCs. By fitting the distribution of relaxation times, it is concluded that the composite cathode material (NBC&BCT2) significantly accelerates the oxygen dissociation and adsorption kinetics compared with NBC. At 700 °C, the symmetric cell with NBC&BCT2 exhibits an area-specific resistance of only 0.034 Ω cm 2 , approximately 23% of that of NBC. When used as the cathode in IT-SOFCs, the NBC&BCT2-based cells achieve a maximum power density of 1.01 W cm 2 at 700 °C, which is 1.4 times higher than that of NBC. Furthermore, composite modification with BCT alleviates the long-term stability drawbacks originating from the excessively high TEC of Co-based materials. Single cells equipped with NBC&BCT2 maintain stable operation over 100 h under a constant rated voltage, with an output current density 1.5 times higher than that of NBC-based cells. This work establishes a reliable modification strategy to promote the electrocatalytic performance of Co-based perovskites and resolve stability limitations induced by high TEC.