mechanism of photocatalytic decomposition of h2o2 on rutile and anatase

The formation, adsorption and degradation of H2O2 on different surface area and nature of commercial TiO2 (anatase, rutile) and on ZnO have been investigated to better understand its participation in the photocatalytic reactions. Langmuir and Langmuir-Hinshelwood models have been used for determining the adsorption constants and the rate constants of H2O2 on these different photocatalysts under dark and under UV-A irradiation respectively. Interaction between H2O2 and TiO2 has been investigated by UV-Vis spectroscopy. Adsorption properties of H2O2 on TiO2 samples are discussed in term of surface and nature of TiO2 but also of the number of OH group present on the photocatalysts. Nature of the yellow complex formed between H2O2 and TiO2 are discussed taking into account its stability, the coverage rate of OH groups, and literature. The kinetics of H2O2 disappearance on the different photocatalysts are argued considering the adsorption properties but also the energy of conduction band of anatase and rutile photocatalysts. The results of the formation and decomposition pf H2O2 under UV-A irradiation in presence of ZnO photocatalyst are explained in light of its adsorption.