Elucidating the Copper–Hägg Iron Carbide Synergistic Interactions for Selective CO Hydrogenation to Higher Alcohols

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.