Metal-supported oxide two-dimensional films represent an interesting class of materials, whose properties depend on the low dimensionality of the film, as well as the interplay with the metal substrate, with relevant implications in many fields. Indeed, the metal-supported oxide thin films display the peculiar property to trigger the electron transfer from the metal substrate to a reactive adsorbate (or vice versa) via tunnelling through the film. This has consequences on the adsorption of single metal adatoms, acting as active species in heterogeneous catalysis or atomic-scale magnets. Aiming at a systematic investigation, we report a comparative DFT study of single (K, Au, and Pt) atoms adsorption over a wide range of metal-supported oxide ultrathin films (MgO on Ag and Mo, ZnO on Cu, Ag, and Au, SiO2 on Pt and Ru, TiO2 on Ag and Pt, ZrO2 on Pt and ZrPt). These films include experimentally studied reducible and non-reducible oxides, showing very unusual and interesting behaviour towards metal atoms adsorption. The interaction of K and Au with the metal/oxide substrates is dominated by charge-transfer aspects, where K tends to assume positive charge and Au negative charge. This fact reflects into a general trend where metal-supported oxide films displaying large work function (i.e. deep empty states) tend to bind K cations strongly, while supports with small work function (i.e. shallow donor states) strongly stabilize Au in anionic form. The correlation between adsorption energy and work function is not strong enough to neglect several other aspects related to chemical and morphological properties of the specific oxide/metal interface. The case of Pt is completely different: here, covalent contributions to the bonding prevail, and the bond strength depends on factors such as the surface morphology and local atomic coordination, rather than the support’s work function.

Computational characterization of single-atom species on metal-supported oxide thin films

ACS Spring Meeting 2021

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