Hydrogen peroxide and photocatalysis

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