η-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 defective η-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 the 3F site. 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 4F site 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 the η-Fe2C(011) surface.

DFT calculations;η-Fe2C; CO adsorption; CO activation费托合成作为煤炭间接液化技术（煤气化后经合成气催化转化为汽油、柴油、石蜡及其他液体产品），是提高煤炭高效洁净利用的重要手段之一。费托合成技术不仅可以大幅降低油品对环境的污染，还可缓解我国过度依赖石油进口的现状，具有重要的国家安全战略意义。