Fine-Tuning the Active Phases of CoFe Alloy Carbides for Boosting Olefin Synthesis from CO2 Hydrogenation

The rational design of highly efficient Co–Fe bimetallic catalysts is highly desirable for CO₂ hydrogenation to olefins as an important alternative for traditional petroleum cracking technology. The treatment of carburization to construct the active phases stands out. Herein, the composition of active CoFe alloy carbide catalysts consisting of χ-(Co_xFe_1–x)₅C₂ and θ-(Co_xFe_1–x)₃C phases was fine-tuned by altering the carburization environment. The synergistic effect between the dual components was optimized to improve the CO₂ activation and C–C coupling capacity. The appropriate carburization degree and phase composition of CoFe alloy carbides are favorable for enhancing the space-time yield (STY) of C₂₊ olefins, up to 328.1 mg g_cat^–1 h^–1 on the CoFe catalyst carburized in H₂/CO = 2 at 320 °C for 8 h. This work provides useful guidelines for regulating product distribution in the design and synthesis of highly efficient catalysts.