OH Radicals and H2O2 Molecules in the Gas Phase Near to TiO2 Surfaces

Abstract

The formation of OH radicals and their diffusion into the gas phase after UV-excitation of TiO₂ in the presence of H₂O has been studied using the very sensitive and selective detection method of laser-induced fluorescence (LIF). The time-resolved evolution of the OH radical concentration has been observed at different pressures and at varying distances between the photocatalytic surface and the detection volume. H₂O₂ has been indirectly detected by LIF. The influence of O₂, hydrocarbons, and excitation laser wavelength on the evolution of both species profiles has been studied in this work. The quantum yield for the formation of OH and H₂O₂ has been estimated by comparison with signals obtained after photolysis of H₂O₂ in the gas phase.