RhFe Alloying Promotes the Efficient and Selective Conversion of Syngas to Ethanol

The direct conversion of syngas to ethanol is a promising route for the sustainable production of value-added chemicals and fuels. While Fe-promoted Rh-based catalysts have long been studied because of their notable activity and selectivity towards ethanol, the nature of Rh-Fe interaction and the catalyst structure under reaction conditions remain poorly understood due to the intrinsic complexity of heterogeneous catalysts prepared by conventional approaches. In this work, we construct well-defined RhFe@SiO2 model catalysts via surface organometallic chemistry (SOMC), composed of small and narrowly distributed nanoparticles supported on silica. Such RhFe@SiO2 catalyst converts syngas into ethanol, reaching an overall selectivity of 38% ethanol among all products at 8.4% CO conversion, while the non-promoted Rh@SiO2 catalyst mostly yields methane (selectivity > 90%) and no ethanol. Detailed in situ XAS and DRIFTS studies reveal that the RhFe@SiO2 catalyst corresponds to an Rh-Fe alloy with ca. 3:1 Rh/Fe ratio alongside residual FeII single site. The alloy is stable under working conditions, promoting high activity and ethanol selectivity.