Mechanism of photodecomposition of H2O2 on TiO2 surfaces under visible light irradiation

Photodecomposition of hydrogen peroxide on TiO2 surfaces under visible irradiation (lambda > 420 nm) was investigated, and an interesting result was found that small organic compounds such as salicylic acid were degraded in the presence of TiO2 and H2O2 under visible irradiation, although either TiO2 or H2O2 alone cannot absorb visible light to decompose H2O2 or small organic compounds. Furthermore, the effects of H2O2 concentration, pH, and the wavelength of irradiation light on the degradation of H2O2 were studied. The photodegradation of H2O2 occurred via a zero-order process, and (OH)-O-. radicals were detected by electron paramagnetic resonance experiments in visible-light-irradiated aqueous TiO2 suspensions. A reaction mechanism for the decomposition of H2O2 on the TiO2 surfaces is proposed involving a photoinduced electron transfer of the surface complexes of =Ti-IV-OOH.