Insights into the hydrogen coverage effect and the mechanism of Fischer-Tropsch to Olefins process on Fe5C2 (510)

Direct production of light olefins from synthesis gas through Fischer-Tropsch to Olefins (FTO) process over iron carbide catalysts is promising. several mechanisms have been proposed to explain the formation of different hydrocarbons on the clean surfaces. However, when these mechanisms were discussed before, the influence of adsorbed surface species, especially surface H on the mechanisms is less understood. Hence, we reported a DFT study on hydrogen coverage effect and the mechanism of FTO process on Fe5C2 (510). It is found that the Fe5C2 (510) surface may be covered with a layer of H in FTO process. The mechanism of Fischer-Tropsch synthesis on the Fe5C2 (510) surface prefers to proceed via the CO insertion mechanism rather than the carbide mechanism in presence of adsorbed H. The optimized C-C coupling pathways feature H-assisted CO coupling pathways in which the CHCHO pathways (Ea =1.15 eV) and the CH2CHO pathways (Ea =1.10 eV) are favorable. The methane formation pathways is an alternative major pa...