(629c) Unravelling the Oxidative Coupling of Methanol on Au(111) Using First-Principles-Based Kinetic Modelling

Using biomass-derived C₁ fragments as building blocks towards higher molecular weight compounds is attractive for diversifying the range of feedstock materials available for chemical synthesis. For instance, biomass-derived methanol can undergo oxidative coupling over gold catalysts thereby yielding methyl-formate, an important precursor in the synthesis of several compounds of commercial interest. Recent experimental work at the “Integrated Mesoscale Architectures for Sustainable Catalysis” Energy Frontier Research Center (IMASC EFRC) at Harvard, has demonstrated that the oxidative coupling of methanol can proceed on O-precovered Au surfaces. To better understand the underlying chemistry, and elucidate the factors that affect selectivity towards methyl-formate (as opposed to oxidation towards e.g. formic acid), we have employed a multiscale approach combining Density Functional Theory (DFT) and kinetic Monte Carlo (KMC) simulation. The kinetic models take into account the different hydrogen abstraction (C-H, O-H cleavage), oxidation and coupling pathways, and are parameterized using DFT calculations and transition state theory (TST) approximations. In addition, the models incorporate information about adsorbate-adsorbate lateral interactions that result in coverage-dependent reaction rates. The simulations reveal the role of the O and OH species in abstracting H, as well as the competition between the different oxidation and coupling routes, and allow us to rationalize the experimental observations.