Methanol O-H Bond Dissociation on H-Precovered Gold Originating from a Structure with a Wide Range of Surface Stability

Gold has been shown to exhibit promising catalytic activity, and understanding the fundamental interactions of reactants and hydrogen atoms on a gold surface is key to gaining insight into hydrogenation reaction mechanisms. In this paper, we report that the adsorption of methanol onto a H-precovered Au(111) surface induces an adsorbate structure, or set of structures, on the surface involving both methanol and hydrogen adatoms with a wide range of stability on the surface. Coadsorption of H/MeOD or D/MeOH indicates H/D exchange between the two surface species, providing evidence that the H-precovered gold surface can dissociate the methanol O-H bond at low temperature (<120 K). These isotopic experiments also demonstrate that hydrogen/deuterium atoms released from a methanol molecule desorb at higher temperatures than hydrogen/deuterium atoms originating from the surface, providing insight into the adsorbate structure(s) present. Additionally, the presence of MeOH on the surface is shown to inhibit the ability of adsorbed MeOD to undergo hydrogen exchange, providing additional clues regarding the exchange reaction mechanism. These phenomena are also shown to exist for ethanol on H-precovered Au(111), suggesting that this behavior may be common to alcohols or species with an O-H functional group in general. These observations give insight into the behavior of the O-H group on a gold surface, which can aid in determining reaction mechanisms and directing future catalytic research.