Multiphase engineering regulation of double perovskite and RP structure heterojunction interfaces for solid oxide fuel cells

In the rigorous testing environment of fuel electrodes, surface-modified and element-doped Sr₂Fe_1.5Mo_0.5O_6-δ (SFMO6) experiences RP phase decomposition, thereby significantly improving performance - an aspect often underexplored and underutilized. Therefore, the design of a multiphase structure with complementary advantages and the exploration of their interactions become crucial. In the present investigation, SFMO6, which has outstanding redox stability, high conductivity, and catalytic activity, was combined with Sr₃Fe_1.8Ni_0.2O_7-δ (SFNO7) in different proportions. SFNO7, characterized by thermodynamic stability, absence of phase transitions, and mixed electrical conductivity, serves as an anode material. XRD results reveal structural stability, with minimal exsolution in a hydrogen environment, and good chemical compatibility. TEM confirms the hetero-interface, while ECR results show a complementary role of D_chem and K_ex values for the two structures. At 800 °C, a composition comprising 70% SFMO6 and 30% SFNO7 demonstrates a notably low polarization resistance (Rp) of 0.12 Ω cm². The maximum power density (MPD) reaches 725.7 mW cm⁻² at 800 °C, a 20% improvement compared to single-phase single-cell counterparts (578.9 and 574.1 mWcm⁻²). This research provides a valuable strategy for the preparation of complementary hetero-interface materials for SOFC anodes and supports the improvement of performance by controlling the decomposition of SFMO6 into the RP phase in a reducing atmosphere.