Methyl Formate Formation during Methanol Conversion over the (111) Ceria Surface

We study methyl formate formation during methanol conversion on the fully oxidized and partially reduced ceria (111) surface using density functional theory. Starting from methanol and formaldehyde adsorbed on the surface, we consider two pathways of methyl formate production. Pathway 1 consists of formaldehyde dehydrogenation followed by oxygen–carbon bond formation. Along pathway 2, the oxygen–carbon bond is established prior to intermediate dehydrogenation. Formaldehyde production is observed at elevated temperature at which we expect both pathways to be energetically attainable on the fully oxidized surface. However, the probability of both reactants being adsorbed next to each other is low. This probability can be increased by the reduction of the surface. The partially reduced ceria surface is modeled by the introduction of an oxygen vacancy in the surface. If formaldehyde adsorbs over a vacancy, both pathways potentially contribute to methyl formate formation. In contrast, if methoxide that is obta...