Rhδ+ Anchored on Rh–Fe Bimetallic Nano-islands Ensures Highly Efficient CO Hydrogenation to Ethanol

Abstract The direct synthesis of ethanol from syngas faces a key challenge: achieving high selectivity at high CO conversion while elucidating the catalytic reaction mechanism. Here, we develop a catalyst comprising highly dispersed Rh–Fe bimetallic nano-islands supported on mixed-phase TiO2, which overcomes the trade-off between catalytic activity and ethanol selectivity, achieving an ethanol selectivity of 62.5% among all carbon-containing products at a CO conversion of 55.8%. Meanwhile, CO2 selectivity is greatly reduced to 8.1%. Mechanistic studies reveal that the breakthrough stems from the enhanced density of interfacial active sites, that the Fe species modulate the local electronic environment to optimize the Rhδ+/Rh0 ratio, and Rhδ+ species in contact with the TiO2 support are stably anchored via the formation of FeOx–Rhδ+–Ov–Ti3+ interfacial sites. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), chemical transient kinetics (CTK), and density functional theory (DFT) characterizations reveal that the surface Rh0 sites facilitate CO dissociation and hydrogenation, whereas the FeOx–Rhδ+–Ov–Ti3+ interfacial sites promote the coupling of CHx with CHxO while suppressing the CO* + O → CO2 pathway. This work provides a route for suppressing CO2 formation and enhancing ethanol production in syngas conversion.