Perovskite Oxyfluoride Electrode Enabling Direct Electrolyzing Carbon Dioxide with Excellent Electrochemical Performances

Solid oxide electrolysis cells (SOECs) can efficiently convert the greenhouse‐gas CO2 to valuable fuel CO at the cathodes. Herein, fluorine is doped into mixed ionic–electronic conducting Sr2Fe1.5Mo0.5O6‐δ (SFM), to evaluate its potential use as a cathode for CO2 reduction reaction (CO2‐RR). SFM retains its cubic structure after doped with fluorine, forming perovskite oxyfluoride Sr2Fe1.5Mo0.5O6‐δF0.1 (F‐SFM). The substitution of oxygen by fluorine increases CO2 adsorption by a factor of ≈2, bulk oxygen vacancy concentration by 35–37% at 800 °C, and consequently enhances the surface reaction rate constant for CO2‐RR and chemical bulk diffusion coefficient by factors of 2–3. The faster kinetics are also reflected by a lower polarization resistance of 0.656 Ω cm2 for F‐SFM than 1.130 Ω cm2 for SFM at 800 °C in symmetrical cells. Furthermore, the single cell with F‐SFM cathode exhibits the best CO2 electrolysis performance among the reported perovskite electrodes, achieving current density of 1.36 A cm−2 at 1.5 V and excellent stability over 120 h at 800 °C under harsh conditions. The theoretical computations confirm that fluorine doping is energetically favorable to CO2 adsorption and dissociation. The present work provides a promising strategy for the design of robust cathodes for direct CO2 electrolysis in SOECs. Solid oxide electrolysis cells are promising energy conversion devices that can efficiently convert CO2 to CO and O2. However, their use is impeded mainly due to the absence of a highly active and durable cathode. This work successfully demonstrates that a SOEC with fluorine‐doped perovskite Sr2Fe1.5Mo0.5O6‐δ cathode enables direct electrolyzing of CO2 with excellent performance and durability.