FNR@FeOx core-shell nanoparticles FNR@FeOx core-shell nanoparticles were formed on the SFMNR electrode within the SFMNR|dense LSGM|SFMNR SOER by annealing at 800 °C for 1 h in H2 (Figure and S11) prior to performance evaluations. When pure C3H8 and CO2 were introduced to the anode and cathode of the SOER at 750 °C, the AC impedance spectrum under open-circuit conditions showed an electrolyte resistance of 0.306 Ω cm² and a polarization resistance of 2.21 Ω cm² (Figure ). Applying 1.6 V generated a substantial current density of 1.3 A cm⁻² (Figure ). The Faradaic efficiency for CO₂ reduction (CO2 + 2e⁻ → CO + O 2 ⁻) was evaluated by measuring the current density and CO production at the cathode via micro gas chromatography (Figure ). At 1500 seconds and an applied voltage of 0.6 V, the SOER produces sufficient CO to calculate the Faradaic efficiency, achieving approximately 90%. Beyond this voltage, CO production shows a nearly linear correlation with current density, with the Faradaic efficiency approaching 100%. Additionally, oxygen transport from the cathode to the anode through the oxide-ion conducting electrolyte was stable over 7200 seconds under cyclic current between 0 and -100 mA cm⁻² (Figure ), indicating efficient propane oxidation and robust oxygen evolution dynamics.