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

We systematically investigated the mechanism of the C1 + C1 coupling reactions using density functional theory. The activation energies of C1 + C1 coupling and carbon hydrogenation reactions on both flat and stepped surfaces were calculated and analyzed. Moreover, the coverages of adsorbed C1 species were estimated, and the reaction rates of all possible C1 + C1 coupling pathways were quantitatively evaluated. The results suggest that the reactions of CH2 + CH2 and CH3 + C at steps are most likely to be the key C1 + C1 coupling steps in FT synthesis on Co catalysts. The reactions of C2 + C1 and C3 + C1 coupling also were studied; the results demonstrate that in addition to the pathways of RCH + CH2 and RCH2 + C, the coupling of RC + C and RC + CH also may contribute to the chain growth after C1.