Fig. 7 shows the results of degradation of MO for different times
during the artificial visible light irradiation of thin films with different
molar ratio of Tu/TiO2. It is clear that S, N-codoping increases the
visible light activity. According to the Fig. 7 with different amounts
of Tu, the photocatalytic activity changes and the film with Tu/TiO2
molar ratio corresponding to 0.45 exhibit the highest photocatalytic
efficiency where 75% MO can be decomposed after visible exposure
for 5 h. While in the presence of undoped TiO2, degradation ratio of
MO is 21% and photodegradation efficiency is small in the absence
of TiO2 film. It is worth mentioning here that the visible light photocatalytic
activity of S, N-codoped TiO2 is much higher than that
of N-only and S-only doped catalysts [2,29].