Fe₃O₄/Fe_1–<i>x</i>S Composites Enable Efficient Asymmetric C–C Coupling for CO₂ Electrocatalytic Reduction to C₂H₆

CO2 electrocatalytic reduction (CO2ER) to multicarbon products is an effective method to reduce carbon emissions and achieve sustainable energy development. However, most CO2ER systems mainly convert CO2 into C1 products, while the main electrocatalysts for generating C2 products (such as C2H4, C2H6, C2H5OH, etc.) are Cu-based materials. Herein, a Fe-based composite (Fe3O4/Fe1–xS) is constructed via in situ sulfidation of Fe2O3. Using 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) acetonitrile (MeCN) solution as the electrolyte, the resultant Fe3O4/Fe1–xS with an optimal component ratio exhibits excellent CO2ER activity and stability with a current density of 35 mA cm–2 and C2H6 Faradaic efficiency (FE(C2H6)) of up to 67.5% at −1.60 V vs Ag/AgCl, which is much higher than the maximum values of pure Fe3O4 (3.5%) and Fe1–xS (36.7%). Experimental and theoretical results demonstrate that [Bmim]PF6 can reduce the activation energy of CO2 molecules and stabilize the *CO intermediate, while the synergistic effect of the electroactive Fe3+-substitution defects (FeFe•) in nonstoichiometric Fe1–xS and the Fe3O4/Fe1–xS interface plays a critical role in promoting the protonation of the *CO intermediate to form *CHO, asymmetric *CO–*CHO coupling, and then continuous dehydration and protonation to generate C2H6. These findings provide valuable insights for improving the CO2ER performance of Fe-based catalysts for the production of multicarbon products.