Improving reversible solid oxide cell performance for CO2 utilization: from enhanced surface reaction kinetics to stable high-current-density operation

Reversible solid oxide cells (RSOCs) demonstrate remarkable advantages in the fields of CO 2 resource utilization and energy transition. The development of highly active fuel electrodes is crucial for boosting the performance of RSOCs. In this work, the perovskite oxide La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 is modified with alkali metal Na and transition metal Mn. This modification effectively increases the oxygen vacancy concentration, as well as enhances its CO 2 adsorption capacity. The results show that Na and Mn doping significantly improves the CO 2 reduction kinetic, surface reaction rate constant ( k chem ) increases by 71.3% from 8.02 × 10 −4 cm s −1 to 13.74 × 10 −4 cm s −1 , and oxygen chemical bulk diffusion coefficient ( D chem ) nearly doubles from 6.34 × 10 −5 cm 2 s −1 to 12.54 × 10 −5 cm 2 s −1 . Therefore, the La 0.55 Sr 0.35 Na 0.1 Co 0.2 Fe 0.7 Mn 0.1 O 3 fuel electrode exhibits superior electrochemical performance, as evidenced by the fact that polarization resistance ( R p ) of the symmetric cell decreases from 1.24 Ω cm 2 to 0.62 Ω cm 2 at 800 °C, which is reduced by half. The La 0.55 Sr 0.35 Na 0.1 Co 0.2 Fe 0.7 Mn 0.1 O 3 fuel electrode enables the single cell to reach a current density of 1063 mA cm −2 at 800 °C and 1.5 V, while delivering the maximum power density ( P max ) of 254 mW cm −2 when operated with a 50%CO–50%CO 2 fuel mixture. In pure CO 2 electrolysis, the cell reaches a current density of 1410 mA cm −2 at 800 °C and 1.5 V, and exhibits outstanding stability over 50 h durability test.