DFT calculations of carbon monoxide adsorbed on anatase TiO2 (101) and (001) surfaces: correlation between the binding energy and the CO stretching frequency

The adsorption of carbon monoxide (CO) on anatase (101) and (001) surfaces was simulated using periodic density functional theory calculations. The surface Lewis acidity was evaluated by computing the binding energy and the adsorbed CO stretching frequency at surface coverages equal to 1 and 0.25 monolayer (ML). The obtained results, in agreement with the experimental data, indicate that the Ti cation of the (101) surface is more electrophilic than that of the (001) surface, corresponding to a larger surface Lewis acidity. A nearly linear correlation between the calculated binding energy and the CO stretching frequency was found for the first time at the computational level. The effects of slab relaxation on the two surfaces were also investigated and an opposite behaviour was found for the two parameters.