Despite the extensive study of the Fe-based Fischer–Tropsch synthesis (FTS) over the past 90 years, its active phases and reaction mechanisms are still unclear due to the coexistence of metals, oxides, and carbide phases presented under realistic FTS reaction conditions and the complex reaction network involving CO activation, C–C coupling, and methane formation. To address these issues, we successfully synthesized a range of pure-phase iron and iron-carbide nanoparticles (Fe, Fe₅C₂, Fe₃C, and Fe₇C₃) for the first time. By using them as the ideal model catalysts on high-pressure transient experiments, we identified unambiguously that all the iron carbides are catalytically active in the FTS reaction while Fe₅C₂ is the most active yet stable carbide phase, consistent with density functional theory (DFT) calculation results. The reaction mechanism and kinetics of Fe-based FTS were further explored on the basis of those model catalysts by means of transient high-pressure stepwise temperature-programmed surface reaction (STPSR) experiments and DFT calculations. Our work provides new insights into the active phase of iron carbides and corresponding FTS reaction mechanism, which is essential for better iron-based catalyst design for FTS reactions.

尽管过去90年来对铁基费托合成（FTS）进行了广泛的研究，但由于在实际FTS反应条件下存在的金属，氧化物和碳化物相共存，其活性相和反应机理仍不清楚。复杂的反应网络，涉及CO活化，CC连接和甲烷形成。为解决这些问题，我们首次成功合成了一系列纯相铁和碳化铁纳米颗粒（Fe，Fe ₅ C ₂，Fe ₃ C和Fe ₇ C ₃）。通过将它们用作高压瞬态实验的理想模型催化剂，我们明确地确定了所有碳化铁在FTS反应中均具有催化活性，而Fe₅ C ₂是最活跃但最稳定的碳化物相，与密度泛函理论（DFT）计算结果一致。在这些模型催化剂的基础上，通过瞬时高压逐步温度程序表面反应（STPSR）实验和DFT计算，进一步探索了铁基FTS的反应机理和动力学。我们的工作为碳化铁的活性相和相应的FTS反应机理提供了新的见解，这对于为FTS反应进行更好的铁基催化剂设计至关重要。