Mechanism of Photodecomposition of H 2 O 2 on TiO 2 Surfaces under Visible Light Irradiation

Photodecomposition of hydrogen peroxide on TiO 2 surfaces under visible irradiation (λ > 420 nm) was investigated, and an interesting result was found that small organic compounds such as salicylic acid were degraded in the presence of TiO 2 and H 2 O 2 under visible irradiation, although either TiO 2 or H 2 O 2 alone cannot absorb visible light to decompose H 2 O 2 or small organic compounds. Furthermore, the effects of H 2 O 2 concentration, pH, and the wavelength of irradiation light on the degradation of H 2 O 2 were studied. The photodegradation of H 2 O 2 occurred via a zero-order process, and • OH radicals were detected by electron paramagnetic resonance experiments in visible-light-irradiated aqueous TiO 2 suspensions. A reaction mechanism for the decomposition of H 2 O 2 on the TiO 2 surfaces is proposed involving a photoinduced electron transfer of the surface complexes of ⋮Ti IV −OOH.