Unraveling the structure sensitivity in methanol conversion on CeO2: A DFT + U study

• Structure sensitivity correlates with the surface oxygen content in the methanol decomposition on ceria.
• Methanol selectively converts to formaldehyde on ceria (1 1 1) and (1 1 0) facets.
• The CeO2(1 0 0) facet traps formaldehyde and ultimately enables its oxidation to produce CO + H2.
• Hydrogen evolution is permitted on (1 0 0) due to its ability to stabilize a hydrogen precursor.
• Formaldehyde can easily exchange its oxygen with the lattice in all facets.

Methanol decomposes on oxides, in particular CeO2, producing either formaldehyde or CO as main products. This reaction presents structure sensitivity to the point that the major product obtained depends on the facet exposed in the ceria nanostructures. Our density functional theory (DFT) calculations illustrate how the control of the surface facet and its inherent stoichiometry determine the sole formation of formaldehyde on the closed surfaces or the more degraded by-products on the open facets (CO and hydrogen). In addition, we found that the regular (1 0 0) termination is the only one that allows hydrogen evolution via a hydride–hydroxyl precursor. The fundamental insights presented for the differential catalytic reactivity of the different facets agree with the structure sensitivity found for ceria catalysts in several reactions and provide a better understanding on the need of shape control in selective processes.

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