Photocatalytic Decomposition of H2O2 on Different TiO2 Surfaces Along with the Concurrent Generation of HO2 Radicals Monitored Using Cavity Ring Down Spectroscopy

Abstract

Hydrogen peroxide (H2O2) is an important reactive oxygen species (ROS) involved in photocatalysis. To study the photocatalytic behavior of H2O2, the decomposition of H2O2 on illuminated TiO2 films was investigated using cavity ring down spectroscopy (CRDS). A mixture of H2O2 and O2 gas was flowed through a cavity reactor which contained a TiO2-coated plate. The removal of H2O2 and the accompanying production of HO2 radicals were monitored in the gas phase just above the TiO2 film which was irradiated by a UV light-emitting diode (LED) (375 nm). The TiO2 films tested in this study were mainly Degussa P25 TiO2 (DP), Aldrich anatase (AA), and Aldrich rutile (AR). The photocatalytic production of HO2 was observed only in the presence of H2O2, which indicates that the HO2 radicals were generated from the decomposition of H2O2, not from the photocatalytic reduction of O2. The direct photolysis of H2O2 in the absence of TiO2 was not observed at all under the present irradiation conditions. The degradation of H2O...