Fluorine-Stabilized BO₆ Octahedron of Host Perovskites for Robust Carbon Dioxide Electrolysis on Exsolved Catalysts

Exsolution of nanoparticles has become a prevalent technique for enhancing the catalytic activity of perovskites for carbon dioxide (CO2) electrolysis in solid oxide electrolysis cells. However, the potential negative impact of phase evolution of the host perovskite on catalytic performance is often overlooked in light of the overall performance enhancement from exsolution. Herein, we illustrate a facile fluorine doping strategy to suppress the phase transition of Sr2Fe1.2Ni0.3Mo0.5O6 -delta (SFN3M) during exsolution. The experimental characterizations combined with density functional theory calculations reveal that the incorporation of fluorine into the SFN3M lattice is beneficial for preserving the high oxidation states of B-site cations and inhibiting the lattice oxygen loss, resulting in a robust BO6 octahedron in the host perovskite. It is found that the well-preserved double perovskite structure exhibits a stronger interaction with CO2, thus enhancing the catalytic activity of F-doped exsolved SFN3M (F-SFN3M-red). Furthermore, the robust BO6 octahedron of the host perovskite significantly enhances the resistance of F-SFN3M-red to decomposition under high-voltage CO2 electrolysis, leading to the significantly increased carbon monoxide productivity over a broad voltage range. These findings highlight that the F doping strategy has great potential to aid the development of exsolved perovskites with high catalytic activity and stability for a wider range of electrocatalysis applications.