Electronic engineering and oxygen vacancy modification of La_0.6Sr_0.4FeO_3- perovskite oxide by low-electronegativity sodium substitution for efficient CO₂/CO fueled reversible solid oxide cells

Reversible solid oxide cells (RSOCs) hold enormous potential for efficient direct CO2 reduction or CO oxidation in terms of exceptional faradic efficiency and high reaction kinetics. The identification of an active fuel electrode is highly desirable for enhancing the performance of RSOCs. This study explores the use of a alkaline metal dopant (Na) to modify the perovskite oxide of Na-2x(La0.6-xSr0.4-x)FeO3-delta (2x = 0, 0.10, 0.20) materials with powerful CO2 chemical adsorption capacity, high oxygen ion conductivity, and low average valence of Fe sites for CO2/CO redox reactions. The experimental results indicate that the cells with the NaLSF0.10 fuel electrode achieve a current density of 1.707 A cm(-2) at 1.5 V/800 degrees C and excellent stability over 120 hours at 750 degrees C for pure CO2 electrolysis, approximately 33.4% improvement over the pristine sample. When operated under a mixed CO-CO2 atmosphere under RSOC mode, the cell outputs the performance of 1.589 A cm(-2) at 1.5 V and 329 mW cm(-2) at 800 degrees C, and demonstrates relatively durable operation over 25 cycles. The addition of low valence sodium ions with high basicity and low electronegativity reduces the oxygen vacancy formation energy, increases the concentration of oxygen vacancies and modifies the electronic structure of LSF, thus enhancing CO2 adsorption, dissociation processes and charge transfer steps as corroborated by the detailed experimental analysis. Combined with the acceptable anti-carbon deposition capability, we prove here a feasible strategy and provide new insights into designing novel electrodes for SOEC/RSOCs to effectively convert CO2 with potential for renewable energy storage.