Promoting catalysis activity with optimizable self-generated Co-Fe alloy nanoparticles for efficient CO₂ electrolysis performance upgrade

Stable and flexible metal nanoparticles (NPs) with regeneration ability are critical for long-term operation of solid oxide electrolysis cells (SOECs). Herein, a novel perovskite electrode with stoichiometric Pr_0.4Sr_0.6Co_0.125Fe_0.75Mo_0.125O_3−δ (PSFCM) is synthesized and studied, which undergoes multiple redox cycles to validate its structural stability and NPs reversibility. The Co-Fe alloy has exsolved from the parent bulk under reducing atmosphere, and is capable of reincorporation into the parent oxide after re-oxidation treatment. During the redox process, we successfully manipulate the size and population density of the exsolved NPs, and find that the average particle size significantly reduces but the population density increases correspondingly. The electrode polarization resistance of the symmetric cell remains stable for 450 h, and even activates after the redox cycling, which may be attributed to the higher quantity and larger specific surface area of the regenerated Co-Fe alloy NPs. Moreover, the electrochemical performance towards carbon dioxide reduction reaction (CO₂RR) is evaluated, and the CO₂ electrolyzer consisting of CoFe@PSCFM-Ce_0.8Sm_0.2O_1.9 (SDC) dual-phase electrode exhibits an excellent current density of 1.42 A·cm⁻² at 1.6 V, which reaches 1.7 times higher than 0.83 A·cm⁻² for the pristine PSCFM electrode. Overall, with this flexible and reversible high-performance SOEC cathode material, new options and perspectives are provided for the efficient and durable CO₂ electrolysis.