Fischer-Tropsch synthesis (FTS) is a structure-sensitive reaction of which performance is strongly related to the active phase, particle size, and exposed facets. Compared with the full-pledged investigation on the active phase and particle size, the facet effect has been limited to theoretical studies or single-crystal surfaces, lacking experimental reports of practical catalysts, especially for Fe-based catalysts. Herein, we demonstrate the facet sensitivity of iron carbides in FTS. As the prerequisite, {202} and {112} facets of χ-Fe₅C₂ are fabricated as the outer shell through the conformal reconstruction of Fe₃O₄ nanocubes and octahedra, as the inner cores, respectively. During FTS, the activity and stability are highly sensitive to the exposed facet of iron carbides, whereas the facet sensitivity is not prominent for the chain growth. According to mechanistic studies, {202} χ-Fe₅C₂ surfaces follow hydrogen-assisted CO dissociation which lowers the activation energy compared with the direct CO dissociation over {112} surfaces, affording the high FTS activity.

费托合成 (FTS) 是一种结构敏感反应，其性能与活性相、粒径和暴露面密切相关。与对活性相和粒径的全面研究相比，面效应仅限于理论研究或单晶表面，缺乏实用催化剂特别是铁基催化剂的实验报告。在这里，我们展示了 FTS 中碳化铁的刻面敏感性。作为前提条件，通过共形重构Fe ₃ O ₄纳米立方体和八面体分别作为内核，制备χ-Fe ₅ C ₂的{202}和{112}面作为外壳。在 FTS 过程中，活性和稳定性对碳化铁的暴露面高度敏感，而面敏感性对于链增长并不突出。根据机理研究，{202} χ-Fe ₅ C ₂表面遵循氢辅助CO解离，与{112}表面上的直接CO解离相比，这降低了活化能，从而提供了高FTS活性。