Visible-light absorption and photocatalytic activity in molybdenum- and nitrogen-codoped TiO2

Nanocrystalline samples of titanium dioxide (TiO2) monodoped or codoped with molybdenum (Mo) and nitrogen (N) were prepared by a sol–gel method. The codoped sample exhibited better absorption performance to visible-light from the absorption spectra, which was understood by the synergistic effect due to Mo and N-doping. However, best photocatalytic activity for degrading methylene blue (MB) was obtained in the N-doped sample instead of the codoped sample. The photocatalytic activity of the codoped sample is slightly better than the pure sample. The possible mechanisms about the optical absorption and photocatalytic properties changes after the dopings were discussed. It was suggested that oxygen vacancies played an important role in the photocatalytic performance of TiO2.