Study on the formation of H2O2 on TiO2 photocatalysts and their activity for the photocatalytic degradation of X-GL dye

Titanium dioxide (TiO2) nanoparticles of both anatase and rutile phases were synthesized by hydrothermal treatment of microemulsions, and their photocatalytic activity for the degradation of X-GL dye was investigated. The only difference between the two methods used was that different acids were added to the microemulsions to make a direct comparison of the photocatalytic activity of the polymorphs possible. UV-Vis reflectance and XRD spectroscopic investigations of these titanium dioxides indicated that a rutile structure could be formed (PR) when hydrochloric acid was used, and anatase formed (PA) when nitric acid was used. The activity of the two polymorphs and P-25 for the photocatalytic degradation of dye in water was also examined. It was found that P-25 consisting of anatase and rutile has the highest activity, and PR consisting of rutile has the lowest. Photodegradation of X-GL in the presence of these different TiO2 particles under air-equilibrated controlled conditions led to the formation of hydrogen peroxide. The formation rate of H2O2 depended on the difference in crystalloid phase. These results indicate that the observed differences in the photocatalytic activity for the three TiO2 photocatalysts are directly related to the formation rate of H2O2.