A quantitative determination of reaction mechanisms from density functional theory calculations: Fischer–Tropsch synthesis on flat and stepped cobalt surfaces

Abstract

We systematically investigated the mechanism of the C 1 + C 1 coupling reactions using density functional theory. The activation energies of C 1 + C 1 coupling and carbon hydrogenation reactions on both flat and stepped surfaces were calculated and analyzed. Moreover, the coverages of adsorbed C 1 species were estimated, and the reaction rates of all possible C 1 + C 1 coupling pathways were quantitatively evaluated. The results suggest that the reactions of CH 2 + CH 2 and CH 3 + C at steps are most likely to be the key C 1 + C 1 coupling steps in FT synthesis on Co catalysts. The reactions of C 2 + C 1 and C 3 + C 1 coupling also were studied; the results demonstrate that in addition to the pathways of RCH + CH 2 and RCH 2 + C, the coupling of RC + C and RC + CH also may contribute to the chain growth after C 1.