A DFT study of CO adsorbed on clean and hydroxylated anatase TiO2 (001) surfaces

The adsorbate-substrate interaction between carbon monoxide and clean and hydroxylated surfaces of anatase (001) was simulated by periodic DFT calculations. For the clean surface, different periodicities were taken into account in order to investigate the influence of lateral effects. The results show that the molecule interacts only with the penta-coordinated titanium ion when high surface coverages are employed, whereas it interacts with both the titanium and the di-coordinated oxygen ions when the smallest surface coverage is considered. Adsorption on the hydroxylated surface, which was carried out for the first time, was studied by considering the largest used periodicity and focusing attention on the influence of both the terminal and bridging OH groups. The resulting data show that, in the case of adsorption on the hydroxylated surface, no additional bond between the surface oxygen and the carbon atom is present. Therefore, in a regime of very low surface coverage, the molecule behaves in a very different way when it interacts with a clean or a hydroxylated surface.