Adsorption of selected ions on the anatase TiO2 (101) surface: a density-functional study

Density-functional calculations of adsorption of the F- and OH- ions on the TiO2 anatase (101) surface have been performed. Changes to the electronic properties prior to and after adsorption have been investigated. The most profound change in the electronic structure of the anatase surface after adsorption is the diminishing of the band gap of the system. While for the pure (without adsorbents) surface the band gap is 1.77eV wide, for the modified surface with the F- and OH- ions the band gap widths equal to 0.35 and 0.39eV, respectively. That means, the excitation energy after adsorption is over four times smaller than in the case of pure system. Nevertheless, in all the cases studied the anatase surface maintains its semiconducting properties.