Coupled A-site regulation and multicomponent B-site substitution in SrFeO3−δ-derived perovskites for active and durable oxygen reduction

Efficient oxygen reduction and long-term structural stability remain difficult to achieve simultaneously in intermediate-temperature solid oxide fuel cells (IT-SOFCs), particularly for conventional SrFeO3-δ-based oxygen electrodes, which suffer from structural instability and performance degradation during prolonged operation. Herein, coupled A-site regulation and multicomponent B-site substitution engineering were implemented by simultaneously regulating the La/Sr ratio at the A site and introducing multicomponent substitution at the B site, yielding a SrFeO3-δ-derived multicomponent perovskite, La0.5Sr0.5Fe0.7Ti0.1Co0.1Mn0.1O3-δ (LSFTCMO-0.5). The optimized composition effectively regulated oxygen-defect chemistry, thereby promoting oxygen-reduction kinetics while simultaneously enhancing structural stability and reducing the thermal expansion coefficient. Consequently, LSFTCMO-0.5 exhibited a low polarization resistance of 0.071 Ω·cm2 at 700 °C and maintained stable electrochemical performance for 200 h. An anode-supported single cell delivered a peak power density of 802 mW·cm-2 at 800 °C and operated stably for over 200 h. Density functional theory calculations revealed that the superior electrochemical performance originates from a balance between oxygen-vacancy formation and oxygen-ion migration. Increasing the Sr content facilitates oxygen-vacancy formation but raises the migration barrier; therefore, the intermediate La/Sr composition provides an optimal compromise between oxygen-vacancy availability and mobility. Differential charge-density analysis further demonstrates that La/Sr regulation modifies the local electronic environment at the migration bottleneck, thereby accounting for the composition-dependent migration barriers. This work establishes coupled A-site regulation and multicomponent B-site substitution engineering as an effective strategy for balancing oxygen-defect thermodynamics and migration kinetics, providing a rational design principle for high-performance oxygen electrodes in IT-SOFCs.