Surface-Templated Assembly of Molecular Methanol on the Thin Film “29” Cu(111) Surface Oxide

Abstract

Identifying and characterizing the atomic-scale interaction of methanol with oxidized Cu surfaces is of fundamental relevance to industrial reactions, such as methanol steam reforming and methanol synthesis. In this work, we examine the adsorption of methanol on the well-defined “29” Cu oxide surface, using a combination of experimental and theoretical techniques, and elucidate the atomic-scale interactions that lead to a unique spatial ordering of methanol on the oxide thin film. We determine that the methanol chain structures form first due to epitaxy with the underlying “29” oxide surface. Specifically, the geometry of the “29” oxide is such that there are spatially adjacent Oδ– sites, in the form of O adatoms, and Cuδ+ species, within the Cu2O-like rings, which allow for methanol to simultaneously bond to the surface via an Omethanol–Cuδ+ dative bond and an OHmethanol–Oδ– hydrogen bond. The methanol–oxide bond strength outweighs the strength of methanol–methanol hydrogen bonds on the “29” Cu oxide, unlike methanol assembly on bare coinage metal surfaces on which hydrogen bonding between adjacent molecules leads to ordered arrays. Weak, long-range interactions lead to the formation of chains of only even numbers of methanol molecules. Together, this work reveals that, unlike that on metal surfaces, the corrugation of the oxide surface drives methanol adsorption to preferred binding sites, preventing intermolecular hydrogen bonding and dictating the adsorption geometry.

In Situ Studies of Methanol Decomposition Over Cu(111) and Cu2O/Cu(111): Effects of Reactant Pressure, Surface Morphology, and Hot Spots of Active Sites

“…This can be attributed to the reduction of the Cu 2 O overlayer by static methoxy and formate, leaving more metallic Cu(111) sites which are highly active in methoxy binding. Methanol exposure to Cu 2 O/Cu­(111) surfaces reduces the oxide at copper metal fronts and forms a CuO x /Cu­(111) oxide/metal interface when heated to 135 K. This is in contrast to low temperature STM studies dosing methanol to Cu 2 O/Cu­(111), which show a nondissociative, molecular adsorption of methanol at 5 K. With this in mind, it can be concluded that the reduction of the Cu 2 O/Cu­(111) in the O 1s data can be attributed to both the reduction of the oxide film and the attenuation by carbon species now on top of the oxide film (Figure S7). The morphology of these areas of reduction are discussed in greater detail in the next section.…”

Quantitative Assessment of Vapor Molecule Adsorption to Solid Surfaces by Flow Rate Monitoring in Microfluidic Channels

“…The average α values obtained for the investigated systems are presented in Table . Hydrogen bonding contributes decisively to the adsorption of alcohol molecules to the oxygen-exposing surfaces. , Surface oxygen species on both PMMA and ZnO serve as potential hydrogen bonding sites for alcohol molecules; adsorbates with higher polarities are more liable to form such bonds. This explains the increasing trend of the obtained adsorption coefficients with the polarity of the alcohol monomers (see Table ).…”

Ordering of Small Molecules on Hydrophobic Self-Assembled n-Alkanethiols: Delicate Balance of Interfacial and Intermolecular Interactions

“…Rather unexpected results for physisorbed assemblies of small molecules have been discovered in recent years using structure-probing diffraction, [20][21][22][23][24] scanning probe, [25][26][27] , and spectroscopic methods. 28,29 Different types of substrate-induced ordering of molecular films have been reported in previous studies in the absence of prominent substrate-molecule interactions. Along the surface normal direction, terraced highly-oriented pyrolytic graphite (HOPG) has been shown to promote ordered stacking of a few small molecules via a lattice-matching template effect, where the step height of the HOPG substrate and the interlayer distance of a nucleating crystal plane can be related in a simple integer ratio.…”