Understanding Heterogeneously Catalyzed Hydrogenation of Carbonyl Compounds Through Keto‐Enol Tautomerization

Abstract The possibility of low‐barrier hydrogenation of carbonyl compounds via keto‐enol tautomerization as the initial step is a highly debated question in catalysis research. Here, a comprehensive description is provided, supported by theoretical and experimental techniques, of surface‐assisted keto‐enol tautomerization and subsequent hydrogenation of carbonyl compounds to alcohols. The crucial role of the ketone‐ketone dimers as key reaction intermediates is elucidated, in which one ketone species undergoes a low‐barrier tautomerization to form a stable ketone‐enol dimer. This phenomenon arises from the strong intermolecular interactions within the dimers and the substantial charge‐transfer between the adsorbates and the surface. Remarkably, the reduction of the barrier is primarily attributed to the charge‐transfer from the inner HOMO−1 orbital. This work explores the atomic details underlying the tautomerization reaction, contributing to the rational design of high‐performance metal catalysts for low‐barrier hydrogenation of carbonyl compounds.