Adsorption and activation of CO onη-Fe2C (011) surface of Fischer-Tropsch synthesis catalyst
Fe2C is discriminated as the active phase of the low-temperature Fischer-Tropsch synthesis (FTS).CO adsorption and activation on this catalyst is the key step during the Fe-based FTS.In order to gain insight to this process, spin-polarized density functional theory calculations were performed to investigate the CO adsorption and activation on both the perfect and defectiveη-Fe2C (011) surfaces.The calculated results show that the most stable configuration of CO adsorption is the top site binding with Fe atom, while the precursor state for CO dissociation is the3Fsite.The direct CO dissociation can hardly occur due to the high CO dissociation barrier, and the H-assisted CO dissociation via HCO intermediate is proposed to be as the dominant activation pathway.Furthermore, with the formation of C-vacant site, the 4Fsite works as the most stable adsorption and activation site, with largely decreases of direct CO dissociation barriers, leading to the similar overall CO activation energy barriers for both direct and H-assisted CO dissociation via formation of HCO.Therefore, they may occur simultaneously with the C-vacant site over theη-Fe2C (011) surface.
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