The relative stability of reactive intermediates, which dictates selectivity of catalytic reactions, is dependent on several factors. It is well known that one factor is the bond strength between the catalyst surface atoms and anchoring atom of intermediates, which can be described by scaling relations for transition metals. Secondary interactions such as van der Waals interactions between the catalyst surface and the pendant group of intermediates also govern the binding hierarchy of some surface-bound intermediates. Herein, we report the identification of molecule-molecule-surface (tertiary) interactions in the oxidative coupling reaction of methanol on Au(110) that lead to the stabilization of molecular methanol by methoxy that can significantly affect the rates of the coupling steps. In this reaction atomic oxygen species on the gold surface activates molecular methanol, producing methoxy species that undergoes coupling to form methyl formate. Experiments using temperature-programmed reaction spectroscopy, scanning tunneling microscopy and high-resolution electron energy loss spectroscopy combined with density functional theory calculations revealed that (1) the activation of methanol by atomic oxygen species occurs as low as 80 K, (2) the methoxy reaction intermediate substantially stabilizes molecular methanol on the surface via hydrogen bonding and (3) co-adsorbed methoxy changes the 2D structure of adsorbed methanol. This work demonstrates a role for surface interactions between adsorbed reaction intermediates and reactant molecules that may affect the selectivity and kinetics of elementary steps in the catalytic reaction network.

Atomic-scale insight into oxidative coupling of methanol on Au(110)

ACS Spring 2022

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