Stabilized Fe₇C₃ catalyst with K-Mg dual promotion for robust CO₂ hydrogenation to high-value olefins

Iron carbide catalysts, particularly the Fe₇C₃ phase, hold significant potential for efficient CO₂ hydrogenation to olefins, yet stabilizing this phase under reactive conditions remains a major challenge. Herein, we report a robust and efficient synthesis of nearly phase-pure Fe₇C₃ catalysts derived from Prussian blue analogues, whose stability is significantly enhanced by strategically incorporating K and Mg promoters. Comprehensive characterization reveals that K accelerates the carbonization process and markedly enhances olefin selectivity, whereas Mg effectively suppresses water-induced oxidation, preserving the structural integrity of the Fe₇C₃ phase. Under optimized reaction conditions (340 °C, 2 MPa, H₂/CO₂ = 3), the Fe₇C₃-KMg catalyst achieves a high CO₂ conversion of 41.5% and an olefin selectivity of 67.1%, maintaining exceptional catalytic stability for over 1000 hours. These findings offer valuable new insights into the rational design of robust iron carbide catalysts for sustainable and efficient CO₂ conversion into high-value chemicals.