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

摘要

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.