A Role for Induced Molecular Polarization in Catalytic Promotion: CO Coadsorbed with K on Co{1010}

The Fischer−Tropsch and higher oxygenate syntheses by hydrogenation of CO were two of the most intensively studied catalytic reactions of the last century, yet a complete understanding of their underlying mechanisms remains elusive. Promotion of the reactions by alkali metal coadsorption is often regarded as being due to enhanced CO dissociation, but a recent experimentally determined surface structure for Co{101̄0}/(K + CO) indicates that more subtle processes may also be involved. This highly unusual structure, having no analogue in three-dimensional chemistry, is now reproduced using first-principles density functional theory. Our analysis of mixed-orbital bonding states demonstrates not only the importance of synergic processes in promoting CO dissociation, but also the existence of a remarkably strong alkali-induced polarization of the C−O bond itself. This polarized bond would be highly reactive in the presence of H 2 . The implications for heterogeneous catalysis in general are profound, since the importance of promoter-induced molecular polarization has hitherto been largely ignored.