Investigation of CHBrF2 adsorbed on TiO2 through IR spectroscopy and DFT calculations

The adsorption of bromodifluoromethane (CHBrF2) on TiO2 has been investigated through IR spectroscopy for the first time. The spectrum of the adsorbed molecule suggests that the compound binds weakly to the surface site preferably through the Br atom. DFT/B3LYP calculations on the possible adsorption structures have been carried out on the anatase (1 0 1) surface simulating the interaction between the five-fold coordinated titanium ion and one of the halogen atoms. In the case of the interaction through the Br atom, the adsorption has been modeled both in presence and in absence of H-bond between the adsorbate and the substrate and only in the first case the calculated binding and interaction energies indicate a favorable adsorption. An attraction between the molecule and the surface in case of adsorption through the F atom is found possible according to the computed interaction energies. The comparison between the observed and calculated vibrational frequencies confirms that the adsorption involves the Br and H atoms. Moreover, it suggests that also the interaction through the F and H atoms is possible. The work shows the importance of the simulation of the possible adsorbate-substrate structures in order to better interpret the experimental data.