TiO2 with sulfur doping

In this project the goal was to understand the extent to which sulfur doping in TiO2 can lead to an increase of the optical absorption. In undoped TiO2 the optical band gap is fairly large and, hence, the absorption is small. It is believed that the photocatalytic activity of the material can be significantly increased if the absorption in the visible spectral range could be increased.

Below (if JAVA works in your web browser) you can see (and rotate) a supercell of TiO2 that contains a total of 96 atoms: 32 titanium atoms (grey), 63 oxygen atoms (red), and one sulfur atom (yellow) on the lattice position of the 64th oxygen atom.

In our study (see. Ref. [1]) we found that not only does the sulfur atom introduce additional optical absorption from defect levels, but it also breaks the crystal symmetry of ideal TiO2, which leads to additional contributions to the optical absorption in the visible spectral range. This, indeed, may increase the photocatalytic activity and render TiO2 an even more versatile material than it already is!