Synergistic defect and doping engineering ensures high-performance symmetric solid oxide cells electrode

Reversible symmetric solid oxide cells (RSSOCs) offer a promising solution for bidirectional electric-hydrogen conversion, enabling integrated energy storage and conversion within a single device. However, their symmetric electrode design, which requires multifunctional catalytic activity, continues to face challenges in terms of both activity and stability. Here, we overcome these challenges by employing an innovative A-site defect and B-site Pd doping strategy in Pr 0.2 Sr 0.8 Co 0.2 Fe 0.8 O 3-δ (PSCF), which results in the in-situ exsolution of B-site metal elements. This approach results in the formation of Pd and Co-Fe nanoparticles, which significantly enhance the electrocatalytic performance of the symmetric electrodes. Electrochemical test shows that defect-engineered PSCFPd with 10 % A-site deficiency achieves a peak power density of 0.830 W cm −2 in fuel cell mode at 850 °C and a current density of 1.64 A cm −2 at 1.5 V in electrolysis mode (50 % H₂O). In addition, the cell demonstrates excellent stability, maintaining performance over 210 h in fuel cell mode and 168 h in electrolysis mode at 800 °C. First-principles calculations further confirm that the defect structure enhances B-site metal migration to the surface, promoting oxygen vacancy formation and mitigating Sr segregation, thereby improving both performance and durability. This work provides a new avenue for the design of high performance electrodes in RSSOCs.