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Zusammenfassung:
The direct conversion of syngas to ethanol is a cornerstone reaction in evolving technologies of CO2 utilization and hydrogen storage, which is typically performed using promoted Rh catalysts. A rational catalyst development requires a detailed structural understanding of the activated catalyst and in particular, the specific roles that promoters play in driving the chemoselectivity of this process. Herein, we report for the first time a comprehensive and comparative atomic‐scale study of metal‐promoter interaction in silica‐supported Rh, Rh‐Mn and Rh‐Mn‐Fe catalysts by aberration‐corrected transmission electron microscopy (AC‐TEM). We uncover that while the catalytic reaction leads to the formation of a Rh carbide phase in the Rh‐Mn/SiO2 catalyst, the addition of Fe results in the formation of bimetallic Rh‐Fe alloys. The latter further improves the selectivity and prevents the carbide formation. In all promoted catalysts, the Mn is present as oxide decorating the metal particles. Based on the atomic insight presented in this work, structural and electronic modifications induced by promoters are revealed and a basis for refined theoretical models is provided.
