Electronic properties of titanium dioxide nanotubes doped with 4d metals

The effect of 4d-metal dopants on the densities of states of hexagonal TiO2 nanotubes has been calculated by the linearized augmented cylindrical wave method. It has been demonstrated that the substitution of Nb, Mo, Tc, or Pd atoms for a part of Ti atoms leads to a decrease in the band gap width of the material due to the formation of impurity levels in the band gap of TiO2. Doping TiO2 nanotubes with these metals is a promising way to produce materials for electrodes for electrochemical photolysis of water. Doping with Y, Rh, or Ag leads to the displacement of the absorption edge from the UV to the visible range owing to a considerable broadening of the valence and conduction band edges; Zr, Ru, and Cd have a lower disturbing effect on the electronic levels of TiO2.