Density functional theory study of the adsorption and reaction of C2H4 on Fe3C(100)

Abstract

Spin-polarized density functional theory (DFT) and a periodic slab model were employed to investigate the adsorption of C 2 H 4 on Fe 3 C(100), which is an active phase of an Fe-based catalyst for Fischer-Tropsch synthesis. The competition between dehydrogenation and cleavage of C 2 H 4 was analyzed. The μ-bridging adsorption mode is more stable than the π or di-σ adsorption modes. Partial rehybridization of the C atoms of C 2 H 4 ( sp 2 → sp 3 ) caused by the interaction of C 2 H 4 with the Fe 3 C(100) surface resulted in the C atoms in C 2 H 4 having a quasi-tetrahedron geometry. On Fe 3 C(100) dehydrogenation of C 2 H 4 occurs, while C-C bond cleavage is not competitive. The calculations indicated that vinylidene (CCH 2 ) and vinyl (CHCH 2 ) species are the most abundant C 2 species, which may be the major monomeric forms of C 2 H 4 in the chain growth in Fischer-Tropsch synthesis DFT calculations indicate that on Fe 3 C(100), C 2 H 4 favors dehydrogenation reaction, while the C-C cleavage is not competitive. Vinylidene (CCH 2 ) and vinyl (CHCH 2 ) are the most abundant.