Selective Oxidation of Methanol to Methyl Formate on Gold: The Role of Low-Coordinated Sites Revealed by Isothermal Pulsed Molecular Beam Experiments and AIMD Simulations

Salma Eltayeb; Lenard L Carroll; Lukas Dippel; Mersad Mostaghimi; Wiebke Riedel; Lyudmila V Moskaleva; Thomas Risse

doi:10.1021/acs.jpcc.4c03959

Selective Oxidation of Methanol to Methyl Formate on Gold: The Role of Low-Coordinated Sites Revealed by Isothermal Pulsed Molecular Beam Experiments and AIMD Simulations

J Phys Chem C Nanomater Interfaces. 2024 Aug 28;128(36):14978-14988. doi: 10.1021/acs.jpcc.4c03959. eCollection 2024 Sep 12.

Authors

Salma Eltayeb¹, Lenard L Carroll^{2

3}, Lukas Dippel¹, Mersad Mostaghimi^{2

4}, Wiebke Riedel¹, Lyudmila V Moskaleva², Thomas Risse¹

Affiliations

¹ Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany.
² Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
³ Institute of Fundamental Physics, Consejo Superior de Investigaciones Científicas, E-28006 Madrid, Spain.
⁴ Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany.

Abstract

To elucidate the role of low-coordinated sites in the partial methanol oxidation to methyl formate (MeFo), the isothermal reactivity of flat Au(111) and stepped Au(332) in pulsed molecular beam experiments was compared for a broad range of reaction conditions. Low-coordinated step sites were found to enhance MeFo selectivity, especially at low coverage conditions, as found at higher temperatures. The analysis of the transient kinetics provides evidence for the essential role of Au _x O _y phases for MeFo formation and the complex interplay of different oxygen species for the observed selectivity. Ab initio molecular dynamic simulations yielded microscopic insights in the formation of Au _x O _y phases on flat and stepped gold surfaces emphasizing the role of low-coordinated sites in their formation. Moreover, associated surface restructuring provides atomic-scale insights which align with the experimentally observed transient kinetics in MeFo formation.