The ε-Fe ₂ C/Cu Interface Synergistically Boosts Highly Selective Fischer–Tropsch Synthesis toward Light Olefins

Traditional Fischer–Tropsch synthesis (FTS) on iron-based catalysts is limited by the Anderson–Schulz–Flory (ASF) distribution, with a maximum theoretical selectivity of 58% for the C 2 –C 4 hydrocarbons, accompanied by substantial methane byproduct formation. Suppressing methane formation while enhancing light olefin selectivity is of great significance, however, it remains a major challenge in this field. Herein, we developed a series of Fe/Cu x @Al 2 O 3 surrounded catalysts, which in situ formed a unique ε-Fe 2 C/Cu interfacial structure during the FTS. The optimized Fe/Cu 3.8 @Al 2 O 3 catalyst achieved 84.7% selectivity toward C 2 –C 4 hydrocarbons, significantly exceeding the ASF distribution limit, with a low CH 4 selectivity of 8.9% and an unprecedented light olefin selectivity of 62.3%. Further investigation and theoretical calculations revealed that in the FTS reaction, CO and H 2 adsorbed and dissociated on the ε-Fe 2 C surface, leading to the formation of CH x and C n H m intermediates through hydrogenation and chain-growth processes. Meanwhile, H* dissociated on the Cu surface migrated to the adjacent ε-Fe 2 C sites via hydrogen spillover. The appropriate supply of H* regulated the hydrogenation and desorption of CH x and C n H m species, simultaneously suppressing CH 4 formation and limiting long-chain hydrocarbons (C 5+ ) production. This work provides valuable insights and strategies for designing advanced FTS catalysts for the highly selective production of light olefins from syngas.