Elucidating the Copper–Hägg Iron Carbide Synergistic Interactions for Selective CO Hydrogenation to Higher Alcohols
2017-06-21T00:00:00Z (GMT) by
CO hydrogenation to higher alcohols (C2+OH) provides a promising route to convert coal, natural gas, shale gas, and biomass feedstocks into value-added chemicals and transportation fuels. However, the development of nonprecious metal catalysts with satisfactory activity and well-defined selectivity toward C2+OH remains challenging and impedes the commercialization of this process. Here, we show that the synergistic geometric and electronic interactions dictate the activity of Cu0–χ-Fe5C2 binary catalysts for selective CO hydrogenation to C2+OH, outperforming silica-supported precious Rh-based catalysts, by using a combination of experimental evidence from bulk, surface-sensitive, and imaging techniques collected on real and high-performance Cu–Fe binary catalytic systems coupled with density functional theory calculations. The closer is the d-band center to the Fermi level of Cu0–χ-Fe5C2(510) surface than those of χ-Fe5C2(510) and Rh(111) surface, and the electron-rich interface of Cu0–χ-Fe5C2(510) due to the delocalized electron transfer from Cu0 atoms, facilitates CO activation and CO insertion into alkyl species to C2-oxygenates at the interface of Cu0–χ-Fe5C2(510) and thus enhances C2H5OH selectivity. Starting from the CHCO intermediate, the proposed reaction pathway for CO hydrogenation to C2H5OH on Cu0–χ-Fe5C2(510) is CHCO + (H) → CH2CO + (H) → CH3CO + (H) → CH3CHO + (H) → CH3CH2O + (H) → C2H5OH. This study may guide the rational design of high-performance binary catalysts made from earth-abundant metals with synergistic interactions for tuning selectivity.