Theoretical exploration of intrinsic facet-dependent CH4 and C2 formation on Fe5C2 particle

A theoretical chemistry approach combining Wulff construction, density functional theory, and microkinetics enables revealing the nature of facet-dependent key elementary reactions on single-phase iron carbide at single particle level, complementary to current limited understanding of this issue in experimental exploration of iron-catalyzed Fischer-Tropsch Synthesis. [Display omitted] •Intrinsic catalysis of a single-phase iron carbide particle in FTS was studied.•Neither too strong nor too weak H adsorption is favorable for CH4 formation.•Coupling of two H-deficient hydrocarbon intermediates is more facile.•The surface (111) and (101-) are kinetically more viable for C2 formation.•CH4 formation is kinetically more facile on surface (010), (110) and (111-). Elucidation of intrinsic working principle of single-phase iron carbide and its facet-dependent catalytic behavior remains a substantial challenge in iron-catalyzed Fischer-Tropsch synthesis. Here, we provided in-depth understanding of the iron carbide phase-dependent and facet-dependent properties on theoretically established Fe5C2 particle model through an approach combining Wulff construction, density functional theory, and microkinetics. We studied two key probe reactions, C2 formation via C1+C1 coupling and CH4 formation, by monitoring surface-dependent thermodynamics and microkinetics. Integration of results thereby allows us to assess the macroscopic catalytic properties at single particle level and evaluate contribution from individual exposed surface. The surface (111) and (101-) are kinetically more viable for C2 formation, whereas CH4 formation is kinetically more facile on surface (010), (110) and (111-). This study enriches the knowledge of the intrinsic working mechanism for single-phase iron carbide and provides fundamental insights into rational design of improved iron-based Fischer-Tropsch synthesis catalysts.