Isothermal molecular beam experiments on the methanol oxidation over the stepped Au(332) surface were conducted under well-defined ultra-high vacuum conditions.

Surface deactivation for partial methanol oxidation to methyl formate on Au(332) under oxygen-deficient conditions at low temperatures suggests a small number of highly active sites for methyl formate formation.

The interaction of molecules with low coordinated sites and possible modification of surfaces caused by adsorbates are of crucial importance for an understanding of chemical processes on surfaces. Herein, CO adsorption on a stepped Au(332) surface is investigated by combining infrared spectroscopy and density functional theory calculations. It is shown that infrared spectroscopic characterization of isotopically diluted mixtures allows distinguishing different components. These components exhibit significantly different adsorption energies as well as vibrational characteristics which can be understood with the help of a theoretical analysis based on density functional theory (DFT). In addition, it is shown that CO induces a restructuring of the surface, leading to a significantly more heterogeneous ensemble of adsorption sites and a significant reduction of sites with the highest CO adsorption energy.

Recent evidence for low-temperature oxidation of methyl formate on Au(332) may affect the selectivity of gold catalysts during partial oxidation of methanol. Under isothermal conditions, overoxidation of methyl formate is...

The oxidation of methyl formate on oxygenprecovered Au(332) was studied by temperature-programmed reaction (TPR) spectroscopy and infrared reflection absorption spectroscopy (IRAS) under well-defined ultrahigh vacuum conditions. Methyl formate was found to bind more strongly and with a significantly altered adsorption geometry upon oxygen precoverage of Au(332) (O/Au(332)) compared to pristine Au(332). TPR experiments evidence oxidation of methyl formate for low oxygen coverage (0.13 ML) at low temperatures. In particular, three discernible channels resulting in CO 2 desorption at 135, 185, and 320 K could be identified. Isotopic labeling experiments with preadsorbed 18 O reveal different ratios of CO 2 isotopologues for the different reaction channels, suggesting different underlying reaction mechanisms, namely, the attack of oxygen to the carbonyl carbon or the methyl carbon of methyl formate. The desorption at 320 K is found to result from the decomposition of formate, which is formed at around 200 K and adsorbs at specific surface sites. The oxidation of methyl formate at low temperatures and low oxygen coverages renders these reaction channels possible pathways to deteriorate the selectivity of catalytic methanol oxidation to methyl formate on gold surfaces.