What is it about?

Carbon monoxide is widely used to identify catalytic sites on titanium dioxide surfaces: according to literature, very active Ti sites correspond to higher CO vibration frequencies. Here we challenge this model and reveal that the vibration frequency of CO results from a donation/backdonation process, where the oxygen anions of the TiO2 surface act as electron density donors.

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Why is it important?

For the first time, we show that the oxygen atoms of oxide surfaces may affect the properties of a molecule not directly linked to them. This “indirect electron donor” character, is intrinsic to the surface, i.e. it exists independently on the presence of defects, and depends on the specific facet. It can be experimentally detected by monitoring the properties of a probe molecule – in this case, its vibration frequencies. Our finding that oxygen atoms of an oxide surface may act as indirect electron density donors is important because it helps to understand the reactivity of molecules at surfaces.


We demonstrate that higher frequencies of adsorbed CO are not necessarily associated to highly reactive sites on TiO2 surfaces. This information is particularly important for understanding how the useful properties of titanium dioxide nanomaterials are related to the microscopic details of the surface, In a broader perspective, this mechanism may hold in general for metal-oxides such as TiO2 and might provide insight to other phenomena where molecule- surface interactions are involved (e.g. reactivity, catalysis, photocatalysis).

Gloria Tabacchi
university of insubria

Read the Original

This page is a summary of: On the Simple Complexity of Carbon Monoxide on Oxide Surfaces: Facet-Specific Donation and Backdonation Effects Revealed on TiO2Anatase Nanoparticles, ChemPhysChem, April 2016, Wiley,
DOI: 10.1002/cphc.201600284.
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