Strong interaction between Fe and Ti compositions for effective CO2 hydrogenation to light olefins

Abstract

Fe-based catalysts are widely used for CO₂ hydrogenation to light olefins (C_2–4⁼); however, precise regulation of active phases and the balance between intermediate reactions remain significant challenges. Herein, we find that the addition of moderate amounts of Ti forms a strong interaction with Fe compositions, modulating the Fe₃O₄ and Fe₅C₂ contents. Enhanced interaction leads to an increased Fe₅C₂/Fe₃O₄ ratio, which in turn enhances the adsorption of reactants and intermediates, promoting CO hydrogenation to unsaturated alkyl groups and facilitating C–C coupling. Furthermore, the strong Fe-Ti interaction induces the preferential growth of Fe₅C₂ into prismatic structures that expose the (020), (–112), and (311) facets, forming compact active interfacial sites with Fe₃O₄ nanoparticles. These facet and interfacial effects significantly promote the synergistic coupling of the reverse water gas shift and Fischer-Tropsch reactions. The optimized 3K/FeTi catalyst with the highest Fe₅C₂/Fe₃O₄ ratio of 3.6 achieves a 52.2% CO₂ conversion rate, with 44.5% selectivity for C_2–4⁼ and 9.5% for CO, and the highest space-time yield of 412.0 mg g_cat^–1 h^–1 for C_2–4⁼.